Coordinated by CRHEA-CNRS research laboratory, this monthly newsletter is produced by Knowmade with collaboration from the managers of GANEX groups. The newsletter presents a selection of newest scientific publications, patent applications and press releases related to III-Nitride semiconductor materials (GaN, AlN, InN and alloys)

All issues on www.ganex.fr in Veille section. Free subscription http://www.knowmade.com/ganex

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Cluster of Excellence (Labex, 2012-2019) GANEX is a cluster gathering French research teams involved in GaN technology. The objective of GANEX is to strengthen the position of French academic players in terms of knowledge and visibility, and reinforce the French industrials in terms of know-how and market share. www.ganex.fr

KnowMade Knowmade is a Technology Intelligence and IP Strategy consulting company involved in Microelectronics, Nanotechnology, Biotechnology and Life Sciences. We provide Patent Search, Patent Landscape, Patent Portfolio Assessment, Patent Infringement Analysis, State of the Art, Scientific Landscape, Technology Scouting, Technology Tracking, Alerts and Updates. Our service offer consists of standard reports, custom studies & on-demand tracking, strategy consulting and training. We combine information search services, scientific expertise, powerful analytics and visualization tools, and proprietary methodologies for analyzing patents and scientific information. Knowmade supports research laboratories, industrial companies and investors in their business development. www.knowmade.com

GANEX Newsletter No. 35 December 2015

III-N Technology

KnowMade

GANEX | Newsletter No. 35 - III-N Technology 2

METHODOLOGY

Each month

250+ new scientific publications

120+ new patent applications

20+ new press releases

Sources 10+ scientific journal editors

Elsevier, IOP, IEEE, Wiley, Springer, APS, AIP, AVS, ECS, Nature, Science …

10+ specialist magazines Semiconductor Today, ElectoIQ, i-micronews,

Compound Semiconductor, Solid State Technology … 5+ open access database: FreeFulPDF, DOAJ …

Patent database: Questel-Orbit

Selection by III-N French

experts

GANEX monthly newsletter

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GANEX | Newsletter No. 35 - III-N Technology 3

TABLE OF CONTENTS (clickable links to chapters)

FOCUS ON EVENT .............................................................................................................................. 4

SCIENTIFIC PUBLICATION ................................................................................................................... 5

GROUP 1 - LEDs and Lighting ................................................................................................................... 5

GROUP 2 - Laser and Coherent sources ................................................................................................... 8

GROUP 3 - Power Electronics ................................................................................................................. 11

GROUP 4 - Advanced Electronics and RF ............................................................................................... 14

GROUP 5 - Sensors and MEMS ............................................................................................................... 21

GROUP 6 - Photovoltaics and Energy harvesting ................................................................................... 24

GROUP 7 - Materials, Technology and Fundamental............................................................................. 25

PRESS RELEASE ................................................................................................................................ 37

PATENT APPLICATION ...................................................................................................................... 49

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GANEX | Newsletter No. 35 - III-N Technology 4

FOCUS ON EVENT

Dear Colleague, We would like to inform you that a special session on "Wide bandgap materials for electron devices" will be organized this year at E-MRS Spring Meeting (Symposium L), May 2nd - 6th, 2016 in Lille (France) Hot topics to be covered by the symposium are the following: SiC homoepitaxy on low-offcut substrates, III-N on silicon : nucleation layer, interface control, Thermal issues in GaN and oxide devices, Integrating Graphene with Nitrides or SiC (direct growth, layer transfer), Selective area growth for new device architectures, Wide-bandgap materials for high performance power inverters, Wide-bandgap materials for MEMS and NEMS, p-type doping by implantation. More information about the conference can be found at: http://www.european-mrs.com/2016-spring-symposium-l-european-materials-research-society The deadline for the abstract submission is : Friday, January 15, 2016 The abstract submission is done through the E-MRS interface directly available on the symposium page. Please also note that the papers will be included in a special issue of Physica Status Solidi We hope to see you all soon at E-MRS in Lille for fruitful presentations and discussions on Wide bandgap materials for electron devices ! Sincerely yours The Organizers (D. Alquier, Y. Cordier and K. Zekentes)

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GANEX | Newsletter No. 35 - III-N Technology 5

SCIENTIFIC PUBLICATION Selection of new scientific articles

GROUP 1 - LEDs and Lighting Group leader: Benjamin Damilano (CRHEA-CNRS)

Information selected by Benjamin Damilano (CRHEA-CNRS)

Carrier-density dependence of photoluminescence from localized states in InGaN/GaN quantum wells in nanocolumns and a thin film N. Shimosako1,a), Y. Inose1, H. Satoh1, K. Kinjo1, T. Nakaoka1, T. Oto1, K. Kishino1,2 and K. Ema1,2 1 Department of Engineering and Applied Sciences, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554, Japan 2 Sophia Nanotechnology Research Center, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554, Japan Journal of Applied Physics Vol. 118, 175702 (2015) http://dx.doi.org/10.1063/1.4935025

We have measured and analyzed the carrier-density dependence of photoluminescence (PL) spectra and the PL efficiency of InGaN/GaN multiple quantum wells in nanocolumns and in a thin film over a wide excitation range. The localized states parameters, such as the tailing parameter, density and size of the localized states, and the mobility edge density are estimated. The spectral change and reduction of PL efficiency are explained by filling of the localized states and population into the extended states around the mobility edge density. We have also found that the nanocolumns have a narrower distribution of the localized states and a higher PL efficiency than those of the film sample although the In composition of the nanocolumns is higher than that of the film.

Enhancement in Output Power of Blue Nitride-Based Light-Emitting Diodes With an Electron Retarded Layer Wang, C.K. ; Chiou, Y.Z. ; Chuang, S.B. Department of Electronic Engineering, Southern Taiwan University of Science & Technology, Tainan, Taiwan Display Technology, Journal of Volume:11 , Issue: 12, Page(s):1005 - 1009

http://dx.doi.org/10.1109/JDT.2015.2460255

In this study, GaN-based blue light-emitting diodes (LEDs) with an electron retarded layer (ERL) were investigated and demonstrated. The external quantum efficiency (EQE) and efficiency droop effect can be effectively improved by introducing the ERL which was attributed to the retard of the electrons rejected into the multiple quantum wells (MQWs). Therefore, the electron overflow effect can be effectively suppressed and carrier distribution can become more uniform in the MQWs. Regarding the thermal effect, the hot-cold factors of LEDs with ERL can achieve a better performance due to the carrier uniform distribution in the MQWs, which is not easily influenced by the temperature. On the other hand, the temperature dependence of the electroluminescence (EL) of LEDs with ERL also can exhibit a better property especially at lower temperature.

Effects of Mesa Size on Current Spreading and Light Extraction of GaN-Based LEDs Horng, R.-H. ; Chen, K.-Y. ; Tien, C.-H. ; Liao, J.-C. Graduate Institute of Precision Engineering, National Chung Hsing University, Taichung, Taiwan Display Technology, Journal of Volume:11 , Issue: 12, Page(s):1010 - 1013 http://dx.doi.org/10.1109/JDT.2015.2461015

The mesa size effect on light extraction efficiency (LEE) of light-emitting diodes (LEDs) was studied in this work. The mesa area size of three kinds of LEDs that were evaluated include: {\hbox {350}}\times{\hbox {950}}~\mu{\hbox {m}}^{2} (small-size embedded electrodes: GaN LED, S-LED), {\hbox {500}}\times{\hbox {950}}~\mu{\hbox {m}}^{2} (medium-size embedded electrodes: GaN LED, M-LED), {\hbox {950}}\times{\hbox {950}}~\mu{\hbox {m}}^{2} (large-size embedded electrodes : GaN LED, L-LED). This paper not only discusses LEE, but

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GANEX | Newsletter No. 35 - III-N Technology 6

current density and heat dissipation performance as well. The output power and light extraction efficiency at {\hbox {700}}~{\hbox {mA/mm}}^{2} for S-LED, M-LED, and L-LED are 555, 485, and 432 mW and 38.1%, 33.4%, and 29.7%, respectively. The best output power and LEE of S-LED is due to the electron-hole recombination rate increasing. This phenomenon is caused by the greatest current spread and heat dissipation potential.

External stress effects on the optical and electrical properties of flexible InGaN-based green light-emitting diodes Ray-Hua Horng,1,3,* Ching-Ho Tien,2 Shih-Hao Chuang,2 Keng-Chen Liu,1 and Dong-Sing Wuu2,4 1Graduate Institute of Precision Engineering, National Chung Hsing University, Taichung 402, Taiwan 2Department of Materials Science and Engineering, National Chung Hsing University, Taichung 402, Taiwan 3Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 701, Taiwan 4Department of Materials Science and Engineering, Da-Yeh University, Changhua 515, Taiwan Optics Express Vol. 23, Issue 24, pp. 31334-31341 (2015) http://dx.doi.org/10.1364/OE.23.031334

Flexible InGaN-based green light emitting diodes (LEDs) were fabricated by transferring epilayer to a flexible polyimide substrate with laser lift-off (LLO) and double-transfer technologies. We present a method of increasing light output power in flexible LEDs without modifying their epitaxial layers. These improvements are achieved by reducing the quantum-confined Stark effect by reducing piezoelectric polarization that results from compressive stress in the GaN epilayer. The compressive stress is relaxed due to the external stress induced by increasing bending displacement of flexible substrate. The light output power of the flexible LED at an injection current of 150 mA is increased by approximately 42.2%, as the external bending went to the case of effective length of 15 mm. The experimental results demonstrated that applying external tensile stress effectively compensates for the compressive strain and changes the piezoelectric field in the InGaN/GaN MQWs region, thereby increases the probability of radiative recombination.

Growth and fabrication of semi-polar InGaN/GaN multi-quantum well light-emitting diodes on microstructured Si (001) substrates Chen Long (陈龙)1,2,3, Payne Justin (裴嘉鼎)2, Strate

Jan (史达特)2, Li Cheng (李成)2, Zhang Jian-Ming (张建明)2, Yu Wen-Jie (俞文杰)1, Di Zeng-Feng

(狄增峰)1 and Wang Xi (王曦)1 1 State Key Laboratory of Functional Materials for Informatics, Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China 2 Shanghai Simæra Incorporated, Shanghai 201800, China Chinese Physics B http://dx.doi.org/10.1088/1674-1056/24/11/118102

Semi-polar (1 − 101) InGaN/GaN light-emitting diodes were prepared on standard electronic-grade Si (100) substrates. Micro-stripes of GaN and InGaN/GaN quantum wells on semi-polar facets were grown on intersecting {111} planes of microscale V-grooved Si in metal–organic vapor phase epitaxy, covering over 50% of the wafer surface area. In-situ optical reflectivity and curvature measurements demonstrate that the effect of the thermal expansion coefficient mismatch was greatly reduced. A cross-sectional analysis reveals low threading dislocation density on the top of most surfaces. On such prepared (1 − 101) GaN, an InGaN/GaN LED was fabricated. Electroluminescence over 5 mA to 60 mA is found with a much lower blue-shift than that on the c-plane device. Such structures therefore could allow higher efficiency light emitters with a weak quantum confined Stark effect throughout the visible spectrum.

Green emission from semipolar InGaN quantum wells grown on low-defect (112¯2) GaN templates fabricated on patterned r-sapphire P. de Mierry*, L. Kappei, F. Tendille, P. Vennéguès, M. Leroux and J. Zuniga-Perez CNRS-CRHEA, Valbonne, France Physica status solidi (b) http://dx.doi.org/10.1002/pssb.201552298

In this article, InGaN/GaN multiple quantum wells (MQWs) grown on low-defect (inline image) GaN templates are investigated by photoluminescence

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GANEX | Newsletter No. 35 - III-N Technology 7

(PL), cathodoluminescence (CL), and transmission electron microscopy (TEM). The emission wavelength is tuned from 450 nm (blue) to 550 nm (green) by varying the TMGa flux in the QWs, while keeping the temperature constant. The In content in the QWs is found to increase with increasing TMGa flux. CL measurements show that the first QW and often the second one emit systematically at wavelengths shorter than the following QWs, while TEM measurements indicate that these first QWs are slightly thinner and display less In content than the rest of the stack. Both observations might be explained by considering that these first QWs grow under larger compressive strain than the subsequent QWs. Furthermore, since TEM shows that misfit dislocations oriented along the [inline image] direction are mainly located at the lower MQW stack interface, i.e., between the first QW and the underlying template, the correlation between TEM and CL points toward a plastic relaxation occurring after the stacking of a sufficiently large number of QWs.

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GANEX | Newsletter No. 35 - III-N Technology 8

GROUP 2 - Laser and Coherent sources Group leader: Bruno Gayral (CEA)

Information selected by Knowmade

2 Gbit/s data transmission from an unfiltered laser-based phosphor-converted white lighting communication system Changmin Lee,1,2 Chao Shen,4 Hassan M. Oubei,4 Michael Cantore,1 Bilal Janjua,4 Tien Khee Ng,4 Robert M. Farrell,1 Munir M. El-Desouki,6 James S. Speck,1 Shuji Nakamura,1,3 Boon S. Ooi,4,5 and Steven P. DenBaars1,3 1Materials Department, University of California, Santa Barbara, California 93106, USA 2changmin_lee@kaust.edu.sa 3Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106, USA 4Computer, Electrical and Mathematical Sciences and Engineering (CEMSE) division, King Abdullah University of Science & Technology (KAUST), Thuwal 23955-6900, Saudi Arabia 6National Center for Nanotechnology, King Abdulaziz City for Science and Technology, Riyadh 11442-6086, Saudi Arabia Optics Express Vol. 23, Issue 23, pp. 29779-29787 (2015) http://dx.doi.org/10.1364/OE.23.029779

We demonstrate data transmission of unfiltered white light generated by direct modulation of a blue gallium nitride (GaN) laser diode (LD) exciting YAG:Ce phosphors. 1.1 GHz of modulation bandwidth was measured without a limitation from the slow 3.8 MHz phosphor response. A high data transmission rate of 2 Gbit/s was achieved without an optical blue-filter using a non-return-to-zero on-off keying (NRZ-OOK) modulation scheme. The measured bit error rate (BER) of 3.50 × 10−3 was less than the forward error correction (FEC) limit of 3.8 × 10−3. The generated white light exhibits CIE 1931 chromaticity coordinates of (0.3628, 0.4310) with a color rendering index (CRI) of 58 and a correlated color temperature (CCT) of 4740 K when the LD was operated at 300 mA. The demonstrated laser-based lighting system can be used simultaneously for indoor broadband access and illumination applications with good color stability.

New frontiers in quantum cascade lasers: high performance room temperature terahertz sources Mikhail A Belkin1 and Federico Capasso2 1 Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX 78712, USA 2 Harvard University, School of Engineering and Applied Sciences, 29 Oxford St., Cambridge, MA 02138, USA Physica Scripta Vol. 90; 118002 http://dx.doi.org/10.1088/0031-8949/90/11/118002

In the last decade quantum cascade lasers (QCLs) have become the most widely used source of mid-infrared radiation, finding large scale applications because of their wide tunability and overall high performance. However far-infrared (terahertz) QCLs have lagged behind in terms of performance and impact due to the inability so far of achieving room temperature operation. Here we review recent research that has led to a new class of QCL light sources that has overcome these limitations leading to room temperature operation in the terahertz spectral range, with nearly 2 mW of optical power and significant tunability, opening up also this region of the spectrum to a wide range of applications. III-nitride disk-in-nanowire 1.2 μm monolithic diode laser on (001)silicon Arnab Hazari1, Anthony Aiello1, Tien-Khee Ng2, Boon S. Ooi2 and Pallab Bhattacharya1 1 Center for Photonics and Multiscale Nanomaterials, Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109, USA 2 Division of Computer, Electrical and Mathematical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia Applied Physics Letters Vol. 107, 191107 (2015) http://dx.doi.org/10.1063/1.4935614

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GANEX | Newsletter No. 35 - III-N Technology 9

III-nitride nanowirediodeheterostructures with multiple In0.85Ga0.15N disks and graded InGaN mode confining regions were grown by molecular beam epitaxy on (001)Si substrates. The aerial density of the 60 nm nanowires is ∼3 × 1010 cm−2. A radiative recombination lifetime of 1.84 ns in the disks is measured by time-resolved luminescence measurements. Edge-emitting nanowire lasers have been fabricated and characterized. Measured values of Jth, T0, and dg/dn in these devices are 1.24 kA/cm2, 242 K, and 5.6 × 10−17 cm2, respectively. The peak emission is observed at ∼1.2 μm. Laser diodes with 353 nm wavelength enabled by reduced-dislocation-density AlGaN templates Mary H. Crawford, Andrew A. Allerman, Andrew M. Armstrong, Michael L. Smith and Karen C. Cross Sandia National Laboratories, Albuquerque, NM 87185, U.S.A Applied Physics Express Vol. 8; 112702 http://dx.doi.org/10.7567/APEX.8.112702

We fabricated optically pumped and electrically injected ultraviolet (UV) lasers on reduced-threading-dislocation-density (reduced-TDD) AlGaN templates. The overgrowth of sub-micron-wide mesas in the Al0.32Ga0.68N templates enabled a tenfold reduction in TDD, to (2–3) × 108 cm−2. Optical pumping of AlGaN hetero-structures grown on the reduced-TDD templates yielded a low lasing threshold of 34 kW/cm2 at 346 nm. Room-temperature pulsed operation of laser diodes at 353 nm was demonstrated, with a threshold of 22.5 kA/cm2. Reduced-TDD templates have been developed across the entire range of AlGaN compositions, presenting a promising approach for extending laser diodes into the deep UV. Spatial inhomogeneities in Al x Ga1−x N quantum wells induced by the surface morphology of AlN/sapphire templates Ute Zeimer1, Joerg Jeschke1, Anna Mogilatenko1,2, Arne Knauer1, Viola Kueller1, Veit Hoffmann1, Christian Kuhn3, Tino Simoneit3, Martin Martens3, Tim Wernicke3, Michael Kneissl1,3 and Markus Weyers1

1 Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav- Kirchhoff-Str. 4, D-12489 Berlin, Germany 2 Humboldt-Universität zu Berlin, Institut für Physik, Newton-Str. 15, D-12489 Berlin, Germany 3 Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstr.36, D-10623 Berlin, Germany Semiconductor Science and Technology Vol. 30; 114008 http://dx.doi.org/10.1088/0268-1242/30/11/114008

The effects of the template on the optical and structural properties of Al0.75Ga0.25N/Al0.8Ga0.2N multiple quantum well (MQWs) laser active regions have been investigated. The laser structures for optical pumping were grown on planar c-plane AlN/sapphire as well as on thick epitaxially laterally overgrown (ELO) AlN layers on patterned AlN/sapphire. Two ELO AlN/sapphire templates were investigated, one with a miscut of the sapphire surface to the m-direction with an angle of 0.25°, the other with a miscut angle of 0.25° to the sapphire a-direction. The MQWs are studied by atomic force microscopy, plan-view cathodoluminescence (CL) at room temperature and 83 K as well as transmission electron microscopy using high-angle annular dark-field imaging and energy-dispersive x-ray spectroscopy. The results are compared to optical pumping measurements. It was found that the surface morphology of the templates determines the lateral wavelength distribution in the MQWs observed by spectral CL mappings. The lateral wavelength spread is largest for the laser structures grown on ELO AlN with miscut to sapphire a-direction caused by the local variation of the MQW thicknesses and the Ga incorporation at macrosteps on the ELO-AlN. A CL peak wavelength spread of up to 7 nm has been found. The MQWs grown on planar AlN/sapphire templates show a homogeneous wavelength distribution. However, due to the high threading dislocation density and the resulting strong nonradiative recombination, laser operation could not be achieved. The laser structures grown on ELO AlN/sapphire show optically pumped lasing with a record short wavelength of 237 nm.

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GANEX | Newsletter No. 35 - III-N Technology 10

Anti-Crossing Effect and Optimization of Waveguide Structure in InGaN/GaN/AlGaN Laser Diode on Sapphire Substrate Dong Churl Kim, Sung Beom Bae, Sung Bock Kim, Young-Ho Ko, Young Ahn Leem, Eun Soo Nam Photonics/Wireless Convergence Components Department, Electronics and Telecommunications Research Institute, 138 Gajeongno, Yuseong-gu, Daejeon 305-700, Republic of Korea Current Applied Physics http://dx.doi.org/10.1016/j.cap.2015.11.005

For optimization of the waveguide in an InGaN/GaN/AlGaN laser diode (LD) on a sapphire substrate, we solved the wave equation of the InGaN/GaN/AlGaN waveguide. Several guided modes in the LD waveguide have been presented and we have shown that an anti-crossing effect between the guided modes is an important phenomenon to understand the complicated behaviour of the modes in the LD waveguide under the variation of structure parameters. By systematically varying the widths of the waveguides of the LD waveguide, we can obtain a useful design category to obtain a high optical confinement factor and a low absorption coefficient for high performance of the LD on a sapphire substrate. Degradation of InGaN based green Laser Diodes: Kinetics and driving forces De Santi, C. ; Meneghini, M. ; Meneghesso, G. ; Zanoni, E. Department of Information Engineering, University of Padova, Italy Fotonica AEIT Italian Conference on Photonics Technologies, 2015 http://dx.doi.org/10.1049/cp.2015.0146

Gallium Nitride based Light Emitting Diodes (LEDs) and Laser Diodes (LDs) are reliable devices which are emerging as the reference technology for light emission in the visible range of the electromagnetic spectrum. At the moment, a lot of effort is spent in order to achieve longer lifetimes for InGaN based green LDs, which could lead to the production of portable and highly miniaturized projection systems. Higher Indium concentration allows to cover the green spectral

region, but leads to an higher defectivity of the active region, thus reducing the efficiency and the reliability of the device. In this paper, we will describe the main driving forces for the device degradation, their effects and the diffusion mechanism possibly responsible for the worsening of the performances, experimentally extracting its coefficient (on average, 5×10−22 cm2/s).

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GANEX | Newsletter No. 35 - III-N Technology 11

GROUP 3 - Power Electronics Group leader: Frédéric Morancho (LAAS-CNRS)

Information selected by Frédéric Morancho (LAAS-CNRS) and Yvon Cordier (CRHEA-CNRS)

Investigation of flat band voltage shift in recessed-gate GaN MOSHFETs with post-metallization-annealing in oxygen atmosphere Jae-Gil Lee1,2, Hyun-Seop Kim1, Jung-Yeon Lee1, Kwang-Seok Seo3 and Ho-Young Cha1 1 School of Electronic and Electrical Engineering, Hongik University, Seoul, Korea 2 Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, TX, USA 3 Department of Electrical and Computer Engineering, Seoul National University, Seoul, Korea Semiconductor Science and Technology Vol. 30; 1150108 http://dx.doi.org/10.1088/0268-1242/30/11/115008

We have investigated the effects of post-metallization-annealing (PMA) in oxygen atmosphere on recessed-gate GaN metal-oxide-semiconductor heterostructure field effect transistors (MOSHFETs). The flat band voltage of MOS is a function of bulk and interface charges in the oxide, which strongly depends on a post-annealing process as well as deposition conditions. A positive threshold voltage shift enabling normally-off operation has been achieved by an O2 PMA process where the GaN MOSHFET employed an ICPCVD SiO2 gate oxide with a Ni/Au metal gate. According to the analysis using energy dispersive x-ray spectroscopy in transmission electron microscopy and x-ray photoelectron spectroscopy, it is suggested that the improved SiO2/GaN interface quality with an enhanced metallic-like Ga level was responsible for the positive shift in threshold voltage. Investigation of gate-diode degradation in normally-off p-GaN/AlGaN/GaN high-electron-mobility transistors M. Ťapajna1,a), O. Hilt2, E. Bahat-Treidel2, J. Würfl2 and J. Kuzmík1 1 Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia 2 Ferdinand-Braun-Institut, Leibniz Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Strasse 4, 12489 Berlin, Germany

Applied Physics Letters Vol. 107, 193506 (2015); http://dx.doi.org/10.1063/1.4935223

Gate diode conduction mechanisms were analyzed in normally-off p-GaN/AlGaN/GaN high-electron mobilitytransistors grown on Si wafers before and after forward bias stresses. Electrical characterization of the gate diodes indicates forward current to be limited by channel electrons injected through the AlGaN/p-GaN triangular barrier promoted by traps. On the other hand, reverse current was found to be consistent with carrier generation-recombination processes in the AlGaN layer. Soft breakdown observed after ∼105 s during forward bias stress at gate voltage of 7 V was attributed to formation of conductive channel in p-GaN/AlGaN gate stack via trap generation and percolation mechanism, likely due to coexistence of high electric field and high forward current density. Possible enhancement of localized conductive channels originating from spatial inhomogeneities is proposed to be responsible for the degradation. Dual-gate AlGaN/GaN MIS-HEMTs using Si3N4 as the gate dielectric Tao Gao1,2, Ruimin Xu2, Kai Zhang1, Yuechan Kong1, Jianjun Zhou1, Cen Kong1, Xun Dong1, Tangsheng Chen1 and Yue Hao3 1 Science and Technology on Monolithic Integrated Circuits and Modules Laboratory, Nanjing Electronic Devices Institute, Nanjing, People's Republic of China 2 Fundamental Science on EHF Laboratory, University of Electronic Science and Technology of China (UESTC), Chengdu, People's Republic of China 3 School of Microelectronics, Xidian University, Xi'an, People's Republic of China Semiconductor Science and Technology Vol. 30; 115010 http://dx.doi.org/10.1088/0268-1242/30/11/115010

We have investigated dual-gate AlGaN/GaN metal-insulator-semiconductor high-electron mobility transistors (MIS-HEMTs) using Si3N4 as the gate dielectric by comparison with single-gate

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GANEX | Newsletter No. 35 - III-N Technology 12

MIS-HEMTs. It is shown that the presence of the second gate induces a slight reduction in the maximum output current, transconductance and breakdown voltage, but with the advantages of 5 dB enhanced power gain and higher f T/f max. Combined with a physics-based device simulation, the breakdown characteristics of the dual-gate device are revealed to be dependent on the second gate. These results demonstrate that the incorporation of dual-gate configuration into the MIS gate is a potential alternative for GaN-based high-power and high-frequency applications. Deep trap-induced dynamic on-resistance degradation in GaN-on-Si power MISHEMTs A. Sasikumar, A.R. Arehart, D.W. Cardwell, C.M. Jackson, W. Sun, Z. Zhang, S.A. Ringel Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH 43210, USA Microelectronics Reliability http://dx.doi.org/10.1016/j.microrel.2015.10.026

Identification and characterization of a single, deep trap causing large increases in the on-resistance of GaN-on-Si power metal-insulator-semiconductor-high electron mobility transistors (MISHEMTs) is reported. This is achieved by using HEMT-based deep level optical spectroscopy (DLOS) and related methods in conjunction with high voltage off-state VDS switching up to 400 V. A trap with an activation energy of ~ EC − 2 eV that is physically located in the drain-access region of the MISHEMT is shown to be the primary source of an increase of the dynamic on-resistance increase by as much as ~ 9 times at 400 V operation. Comparisons of trap signatures extracted from the MISHEMT with capacitance-based DLOS measurements of simple Schottky-diode test-structures showing the same, dominant trap signature suggests that the physical defect is located within the GaN buffer and is not a surface or insulator-related defect. A buffer trap based model is presented to explain the observed on-resistance degradation effects in the MISHEMTs during high voltage switching. Advances in Power Conversion and Drives for Shipboard Systems Wang, F. Zhang, Z. ; Ericsen, T. ; Raju, R. ; Burgos, R. ; Boroyevich, D.

Dept. of Electr. Eng. & Comput. Sci., Univ. of Tennessee, Knoxville, TN, USA Proceedings of the IEEE http://dx.doi.org/10.1109/JPROC.2015.2495331

This paper presents some of the key advances in power electronics pertaining to shipboard electric power system applications. The focus is on the emerging wide bandgap semiconductor devices, i.e., silicon carbide (SiC) and gallium nitride (GaN) devices, and their potential impact on future shipboard power conversion and drives. Their benefits on power converter efficiency and power density are explained through a case study of a medium-voltage (MV) class motor drive system. SiC and GaN also enable new applications, including solid-state transformers, while posing new design and application challenges such as gate drive, protection, and interaction with loads. In addition to device related topics, this paper also overviews other important advances in power electronics, including topology, control, passive components, thermal management, filters, and packaging. The significance of power electronics building blocks (PEBBs) concept for shipboard power system development is discussed. Recognizing the growing complexity of shipboard power systems, some system-level technologies related to future MV direct current (dc) system architecture are highlighted. A 13.56MHz class e power amplifier for inductively coupled DC supply with 95% power added efficiency (PAE) Stubenrauch, F. ; Seliger, N. ; Schustek, M. ; Lebedev, A. ; Schmitt-Landsiedel, D. University of Applied Sciences Rosenheim, 83024 Rosenheim RFID Technology (EURFID), 2015 International EURASIP Workshop on http://dx.doi.org/10.1109/EURFID.2015.7332390

Recent development of GaN power transistors with blocking voltages up to 650V enables novel power electronics applications with outstanding performance in high-frequency operation. This paper demonstrates a class E power amplifier with 13.56MHz switching frequency for inductively coupled DC power supplies. Continuous wave

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GANEX | Newsletter No. 35 - III-N Technology 13

output power up to 200W is achieved with 95% Power Added Efficiency (PAE). N-Polar GaN MIS-HEMTs on Sapphire With High Combination of Power Gain Cutoff Frequency and Three-Terminal Breakdown Voltage Zheng, X. ; Guidry, M. ; Li, H. ; Ahmadi, E. ; Hestroffer, K. ; Romanczyk, B. ; Wienecke, S. ; Keller, S. ; Mishra, U. Department of Electrical and Computer Engineering, University of California, Santa Barbara, CA 93106 USA. Electron Device Letters, IEEE http://dx.doi.org/10.1109/LED.2015.2502253

N-polar SiNx/AlGaN/GaN/AlGaN metal-insulatorsemiconductor high-electron-mobility transistors (MIS-HEMTs) with 28.6 nm equivalent GaN channel thickness grown by metal-organic chemical vapor deposition on sapphire substrate with a high combination of current/power gain cutoff frequencies (fT/fmax) and three-terminal breakdown voltage (BVDS) are demonstrated. fT/BVDS of 103 GHz/114 V and fmax/BVDS of 248 GHz/114 V were achieved in devices with gate widths of 2 × 50 μm and 2 × 25 μm respectively, comparing well to recent reports of fully-passivated and vertically-scaled Ga-polar GaN HEMTs. Devices with gate width of 2 × 75 μm showed peak output power densities of 5.74 W/mm at 4 GHz and 6.29 W/mm at 10 GHz obtained by load-pull measurements. Influence of AlN nucleation layer on vertical breakdown characteristics for GaN-on-Si J. J. Freedsman1,*, A. Watanabe1, Y. Yamaoka1, T. Kubo1 and T. Egawa1,2 1Research Centre for Nano Devices and Advanced Materials, Nagoya Institute of Technology, Nagoya, Japan 2Innovation Centre for Multi-Business of Nitride Semiconductors, Nagoya Institute of Technology, Nagoya, Japan Physica status solidi (a) http://dx.doi.org/10.1002/pssa.201532601

A study of metal-organic chemical vapor deposition (MOCVD) grown AlN nucleation layer (NL) on breakdown characteristics for GaN-on-Si is presented. It is widely believed that AlN NL can act as an insulator because of its large band gap

∼6.2 eV. On contrary, this study of AlN NL/Si reveals conductive nature and shows high vertical leakage. The structural examinations along with electrical characterization show AlN NL/Si quality depends on the growth temperature. The surface morphology and presence of unintentional oxygen impurities govern the vertical leakage of AlN NL/Si. Interestingly, the AlN NL influences the growth of subsequent epitaxial layers as well as their vertical breakdown voltages (BVs). Further, it is found that AlGaN intermediate layer and multipairs of AlGaN/AlN strained layer superlattice (SLS) grown over AlN NL with better surface properties enhances the vertical BV. A high BV of 1.3 kV is achieved for SLS multipairs with a total thickness of 4.4 μm and the translated breakdown field strength is 2.8 MV cm−1 for MOCVD grown GaN-on-Si. Comparison of electrical characteristics between AlGaN/GaN and lattice-matched InAlN/GaN heterostructure Schottky barrier diodes Jian Ren, Dawei Yan, Yang Zhai, Wenjie Mou, Xiaofeng Gu, Key Laboratory of Advanced Process Control for Light Industry (Ministry of Education), Department of Electronic Engineering, Jiangnan University, Wuxi 214122, China Microelectronics Reliability http://dx.doi.org/10.1016/j.microrel.2015.11.005

Lattice-matched Pt/Au–In0.17Al0.83N/GaN hetreojunction Schottky barrier diodes (SBDs) with circular planar structure have been fabricated. The electrical characteristics of InAlN/GaN SBD, such as two-dimensional electron gas (2DEG) density, turn-on voltage, Schottky barrier height, reverse breakdown voltage and the forward current-transport mechanisms, are investigated and compared with those of a conventional AlGaN/GaN SBD. The results show that, despite the higher Schottky barrier height, more dislocations in InAlN layer causes a larger leakage current and lower reverse breakdown voltage than the AlGaN/GaN SBD. The emission microscopy images of past-breakdown device suggest that a horizontal premature breakdown behavior attributed to the large leakage current happens in the InAlN/GaN SBD, differing from the vertical breakdown in the AlGaN/GaN SBD.

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GANEX | Newsletter No. 35 - III-N Technology 14

GROUP 4 - Advanced Electronics and RF Group leader: Jean-Claude Dejaeger (IEMN)

Information selected by Jean-Claude Dejaeger (IEMN) and Yvon Cordier (CRHEA-CNRS)

Charge control in N-polar InAlN high-electron-mobility transistors grown by plasma-assisted molecular beam epitaxy Matthew T. Hardy1,a), David F. Storm2, Brian P. Downey2, D. Scott Katzer2, David J. Meyer2, Thomas O. McConkie3 and David J. Smith3 1 Naval Research Laboratory, 4555 Overlook Avenue SW, Washington DC 20375 2 Electronics Science & Technology Division, Naval Research Laboratory, 4555 Overlook Avenue SW, Washington DC 20375 3 Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 Journal of Vacuum Science & Technology B Vol. 33, 061207 (2015); http://dx.doi.org/10.1116/1.4935130

N-polar InAlN-based high-electron-mobility transistors (HEMTs) have fundamental advantages relative to conventional Ga-polar AlGaN HEMTs for high frequency devices. An understanding of the epitaxial design space for controlling sheet carrier density (n s) and mobility (μ) is desirable to maximize power and frequency performance by improving breakdown voltage and reducing parasitic access resistance. In this work, the authors show that In0.17 Al 0.83N barrier thickness has a minimal impact on n s and μ, and an AlGaN cap layer decreases both n s and μ. Optimization of AlN and GaN interlayers can be used to maximize μ and set n s in the range of 1–3 × 1013 cm−2. The authors use this approach to demonstrate N-polar HEMTs grown on freestanding GaN substrates with sheet resistance R s = 190 Ω/◻ and μ = 1400 cm2/V·s, leading to a maximum drain current density of 1.5 A/mm for HEMTs with a 5-μm source–drain spacing and Pt-based Schottky gates. Strain-effect transistors: Theoretical study on the effects of external strain on III-nitride high-electron-mobility transistors on flexible substrates Shahab Shervin1,2, Seung-Hwan Kim1, Mojtaba Asadirad1,2, Srikanth Ravipati1, Keon-Hwa Lee1, Kirill Bulashevich3 and Jae-Hyun Ryou1,2,4,a)

1 Department of Mechanical Engineering, University of Houston, Houston, Texas 77204-4006, USA 2 Materials Science and Engineering Program, University of Houston, Houston, Texas 77204, USA 3 STR Group, Inc., Engels av. 27, P.O. Box 89, 194156, St. Petersburg, Russia 4 Texas Center for Superconductivity at the University of Houston (TcSUH), University of Houston, Houston, Texas 77204, USA Applied Physics Letters Vol. 107, 193504 (2015); http://dx.doi.org/10.1063/1.4935537

This paper presents strain-effect transistors (SETs) based on flexible III-nitride high-electron-mobility transistors(HEMTs) through theoretical calculations. We show that the electronic band structures of InAlGaN/GaN thin-film heterostructures on flexible substrates can be modified by external bending with a high degree of freedom using polarizationproperties of the polar semiconductor materials. Transfer characteristics of the HEMT devices, including threshold voltage and transconductance, are controlled by varied external strain. Equilibrium 2-dimensional electron gas(2DEG) is enhanced with applied tensile strain by bending the flexible structure with the concave-side down (bend-down condition). 2DEG density is reduced and eventually depleted with increasing compressive strain in bend-up conditions. The operation mode of different HEMT structures changes from depletion- to enchantment-mode or vice versa depending on the type and magnitude of external strain. The results suggest that the operation modes and transfer characteristics of HEMTs can be engineered with an optimum external bending strain applied in the device structure, which is expected to be beneficial for both radio frequency and switching applications. In addition, we show that drain currents of transistors based on flexible InAlGaN/GaN can be modulated only by external strain without applying electric field in the gate. The channel conductivity modulation that is obtained by only external strain proposes an

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GANEX | Newsletter No. 35 - III-N Technology 15

extended functional device, gate-free SETs, which can be used in electro-mechanical applications. GaN High-Electron-Mobility Transistor with WN x /Cu Gate for High-Power Applications Ting-En Hsieh, Yueh-Chin Lin, Fang-Ming Li, Wang-Cheng Shi, Yu-Xiang Huang, Wei-Cheng Lan, Ping-Chieh Chin, Edward Yi Chang 1. Department of Materials Science and Engineering, National Chiao-Tung University, Hsinchu, 30010, Taiwan, ROC 3. Institute of Photonic System, National Chiao-Tung University, Tainan, 71150, Taiwan, ROC 2. Department of Electronics Engineering, National Chiao-Tung University, Hsinchu, 30010, Taiwan, ROC Journal of Electronic Materials Volume 44, Issue 12, pp 4700-4705 http://dx.doi.org/10.1007/s11664-015-4118-5

A GaN high-electron-mobility transistor (HEMT) with WN x /Cu gate for high-power applications has been investigated. The direct-current (DC) characteristics of the device are comparable to those of conventional Ni/Au-gated GaN HEMTs. The results of high-voltage stress testing indicate that the device is stable after application of 200 V stress for 42 h. The WN x /Cu-gated GaN HEMT exhibited no obvious changes in the DC characteristics or Schottky barrier height before and after annealing at 250°C for 1 h. These results demonstrate that the WN x /Cu gate structure can be used in a GaN HEMT for high-power applications with good thermal stability Analysis and modelling of GaN Schottky-based circuits at millimeter wavelengths D Pardo and J Grajal Department of Signals, Systems and Radiocommunications, Universidad Politécnica de Madrid, E.T.S.I. Telecomunicación, Av. Complutense 30. 28040 Madrid, Spain Semiconductor Science and Technology Vol. 30; 115016 http://dx.doi.org/10.1088/0268-1242/30/11/115016

This work presents an analysis of the capabilities of GaN Schottky diodes for frequency multipliers and mixers at millimeter wavelengths. By using a Monte Carlo (MC) model of the diode coupled to a harmonic balance technique, the electrical and

noise performances of these circuits are investigated. Despite the lower electron mobility of GaN compared to GaAs, multipliers based on GaN Schottky diodes can be competitive in the first stages of multiplier chains, due to the excellent power handling capabilities of this material. The performance of these circuits can be improved by taking advantage of the lateral Schottky diode structures based on AlGaN/GaN HEMT technology. Impact of oxygen plasma treatment on the dynamic on-resistance of AlGaN/GaN high-electron-mobility transistors Joel T. Asubar1, Yoshiki Sakaida1, Satoshi Yoshida1, Zenji Yatabe2, Hirokuni Tokuda1, Tamotsu Hashizume2 and Masaaki Kuzuhara1 1 Graduate School of Engineering, University of Fukui, Fukui 910-8507, Japan 2 Research Center for Integrated Quantum Electronics, Hokkaido University, Sapporo 060-8628, Japan Applied Physics Express Vol. 8; 111001 http://dx.doi.org/10.7567/APEX.8.111001

We studied the effects of pre-passivation oxygen plasma treatment of the AlGaN surface on the current collapse of AlGaN/GaN high-electron-mobility transistors (HEMTs). Oxygen plasma-treated devices generally exhibited significantly less dynamic on-resistance (Ron) compared with untreated control devices. We also extended our investigation to HEMTs with a GaN cap layer. Interestingly, after oxygen plasma treatment, we found that GaN-capped HEMTs showed a dynamic Ron behavior that was essentially similar to that of oxygen plasma-treated uncapped HEMTs, suggesting that the GaN cap layer plays an inconsequential role in current collapse mitigation when employed in conjunction with oxygen plasma treatment. Thermal Characterization Using Optical Methods of AlGaN/GaN HEMTs on SiC Substrate in RF Operating Conditions Baczkowski, L. ; Jacquet, J. ; Jardel, O. ; Gaquiere, C. ; Moreau, M. ; Carisetti, D. ; Brunel, L. ; Vouzelaud, F. ; Mancuso, Y.

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GANEX | Newsletter No. 35 - III-N Technology 16

Institut d’electronique de Micro electronique et de Nanotechnologie, University of Lille, Villeneuve d’Ascq, France Electron Devices, IEEE Transactions on Volume:62 , Issue: 12, Page(s):3992 - 3998 http://dx.doi.org/10.1109/TED.2015.2493204

Performance and reliability of wide bandgap high-power amplifiers are correlated with their thermal behavior. Thermal model development and suitable temperature measurement systems are necessary to quantify the channel temperature of devices in real operating conditions. As a direct temperature measurement within a channel is most of the time not achievable, the common approach is to measure the device temperature at different locations close to the hotspot and then to use simulations to estimate the channel temperature. This paper describes a complete thermal characterization of AlGaN/gallium nitride (GaN) on silicon carbide high electron-mobility transistors (HEMTs) when devices are operating in dc bias, pulsed, and continuous wave. Infrared thermography, charge-coupled device-based thermoreflectance microscopy, and micro-Raman spectroscopy have been performed to extract the thermal resistance of the components. Results have been compared with simulations using a 3-D finite-element model to estimate the operating channel temperature. Measurements have shown that the RF-biased thermal resistance and the dc-biased thermal resistance of GaN HEMTs are similar. Admittance–voltage profiling of AlxGa1−xN/GaN heterostructures: Frequency dependence of capacitance and conductance K. Köhler1, W. Pletschen1, B. Godejohann1, S. Müller1, H. P. Menner1 and O. Ambacher1 1 Fraunhofer-Institut für Angewandte Festkörperphysik, Tullastraße 72, 79108 Freiburg, Germany Journal of Applied Physics Vol. 118, 205702 (2015) http://dx.doi.org/10.1063/1.4936125

Admittance–voltage profiling of AlxGa1−xN/GaN heterostructures was used to determine the frequency dependent capacitance and

conductance of FET devices in the frequency range from 50 Hz to 1 MHz. The nominally undoped low pressure metal-organic vapor-phase epitaxy structures were grown with an Al-content of 30%. An additional 1 nm thick AlN interlayer was placed in one structure before the Al0.3Ga0.7N layer growth. For frequencies below 108 Hz it is convenient to use equivalent circuits to represent electric or dielectric properties of a material, a method widely used, for example, in impedance spectroscopy. We want to emphasize the relation between frequency dependent admittance–voltage profiling and the corresponding equivalent circuits to the complex dielectric function. Debye and Drude models are used for the description of the frequency dependent admittance profiles in a range of depletion onset of the two-dimensional electron gas. Capacitance- and conductance-frequency profiles are fitted in the entire measured range by combining both models. Based on our results, we see contributions to the two-dimensional electron gas for our samples from surface states (80%) as well as from background doping in the Al0.3Ga0.7N barriers (20%). The specific resistance of the layers below the gate is above 105 Ω cm for both samples and increases with increasing negative bias, i.e., the layers below the gate are essentially depleted. We propose that the resistance due to free charge carriers, determined by the Drude model, is located between gate and drain and, because of the AlN interlayer, the resistance is lowered by a factor of about 30 if compared to the sample without an AlN layer. The Characterization of InAlN/AlN/GaN HEMTs Using Silicon-on-Insulator (SOI) Substrate Technology Hsien-Chin Chiua,z, Li-Yi Penga, Hou-Yu Wanga, Hsiang-Chun Wanga, Hsuan-Ling Kaoa, G.-Y. Leeb and Jen-Inn Chyi aDepartment of Electronics Engineering, Chang Gung University, Taoyuan, Taiwan bDepartment of Electrical Engineering, National Central University, Jhongli 32001, Taiwan Journal of Electrochemical Society Volume 163, issue 2, H110-H114 http://dx.doi.org/10.1149/2.0931602jes

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GANEX | Newsletter No. 35 - III-N Technology 17

The microwave and low frequency noise characteristics of 6 inch InAlN/AlN/GaN high electron mobility transistor (HEMT) were demonstrated and investigated on silicon-on-insulator (SOI) substrate for the first time. The InAlN HEMT on SOI substrate was grown by metal organic chemical vapor deposition (MOCVD) on a p-type (111) Si SOI substrate with a p-type (100) Si handle wafer for possible heterogeneous integration. The Raman spectroscopy measurement indicates that the smaller epitaxy stress was obtained by adopting SOI wafer and X-ray diffraction measurements revealed that InAIN HEMT on SOI achieves a flat surface and an abrupt heterointerface. The InAlN HEMT on SOI exhibits a lower leakage current compared to the device on high resistivity (HR) Si substrate and thus improves the off-state breakdown voltage from 134 V to 198 V. Moreover, the buried SiO2 in SOI substrate also efficiently suppresses the signal loss resulting in the better bandwidth and the microwave power performance. Based on the low frequency noise measurement, InAlN HEMT on SOI substrate also performs a relatively slight degradation after hot carrier stress. Scaling DC lifetests on GaN HEMT to RF conditions Bruce M. Paine Technology Qualification, Boeing Network and Space Systems, El Segundo CA, USA Microelectronics Reliability http://dx.doi.org/10.1016/j.microrel.2015.09.024

The assumptions behind a new lifetesting approach are documented, evaluated, and tested where possible. This approach utilizes “signature parameters” to track individual degradation mechanisms in both DC and RF lifetests, and determines the mean time to failure (MTTF) Arrhenius curves for each mechanism individually, during RF operation. This is important for GaN HEMT because most studies indicate that several mechanisms contribute to its wearout, simultaneously, and this makes it impossible to extrapolate conventional RF wearout curves to other temperatures or longer times. A key assumption is that degradation mechanisms can be identified, and associated with unique

signature parameters. A second key assumption is the integrity of degradation mechanisms, whether they occur under steady DC biases, or under oscillating RF biases. This allows us to deduce MTTF's under RF operation from the ratio of degradation rates of the individual mechanisms in DC lifetests, and the rates in RF operation, integrated over the RF waveform. This can be found by means of DC and RF lifetests, monitoring the signature parameters. Then the DC Arrhenius curves can be scaled to the RF conditions. After evaluation of these, and several other assumptions, we find the net uncertainties for one of the GaN HEMT technologies that we used for development of our approach. They amount to — 30%, + 100% in MTTF; this is entirely adequate for high-reliability parts evaluation, where a margin of at least 10 × (900%) is required. Suppression of Current Collapse in Enhancement Mode AlGaN/GaN High Electron Mobility Transistors Wang, C. ; Ho, S. ; Huang, J. Institute of Photonics and Optoelectronics, National Taiwan University, Taipei 10617, Taiwan Electron Device Letters, IEEE http://dx.doi.org/10.1109/LED.2015.2498623

The phenomenon of current collapse was investigated on p-GaN/AlGaN/GaN enhancement-mode high electron mobility transistors. Contrary to our original thought of carrier depletion on the p-GaN/AlGaN/GaN layers so that less carrier traps, current collapse was observed from such a device without surface passivation. The results were compared with the device passivated with SiO2 dielectric, which showed much less severe current collapse within the gate bias of -15V. To understand the mechanism of dielectric passivation, the capacitance-voltage measurement was performed. Our results show donor-like dislocations in the SiO2/GaN interface help to deplete carriers on the device surface and within the p-GaN, thus maintaining channel carriers and mitigating current collapse.

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GANEX | Newsletter No. 35 - III-N Technology 18

A Reactively Matched 1.0–11.5 GHz Hybrid Packaged GaN High Power Amplifier Barisich, G.C. ; Ulusoy, A.C. ; Gebara, E. ; Papapolymerou, J. School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA, USA Microwave and Wireless Components Letters, IEEE http://dx.doi.org/10.1109/LMWC.2015.2495195

An ultra-wideband PA using a single GaN die with resistive and reactive matching is fabricated and measured. The design includes series and shunt elements at the gate for stability and gain compensation, and uses two different substrates to obtain optimum {\rm Z} _{0} ranges for the matching networks. CW measurements at 31 dBm source power show 27–48% PAE and 35.1–37.4 dBm output power from 1.0 to 11.5 GHz (168% relative bandwidth). These results demonstrate multi-watt output power and high PAE over a decade bandwidth, achieving the best results in this frequency range for a hybrid implementation. AlGaN/GaN high electron mobility transistor with Al2O3+BCB passivation

Zhang Sheng (张昇)1,2, Wei Ke (魏珂)2,3, Yu Le

(余乐)1,2, Liu Guo-Guo (刘果果)2, Huang Sen (黄森)2,

Wang Xin-Hua (王鑫华)2, Pang Lei (庞磊)2, Zheng Ying-

Kui (郑英奎)2, Li Yan-Kui (李艳奎)2, Ma Xiao-Hua

(马晓华)1,4, Sun Bing (孙兵)2 and Liu Xin-Yu (刘新宇)2

1 School of Advanced Materials and Nanotechnology, Key Laboratory of Wide Bandgap Semiconductor Materials and Devices, Xidian University, Xi'an 710071, China 2 Microwave Device and IC Department, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China Chinese Physics B http://dx.doi.org/10.1088/1674-1056/24/11/117307

In this paper, A12O3 ultrathin film used as the surface passivation layer for AlGaN/GaN high electron mobility transistor (HEMT) is deposited by thermal atomic layer deposition (ALD), thereby avoiding plasma-induced damage and erosion to the surface. A comparison is made between the surface passivation in this paper and the conventional plasma enhanced chemical vapor

deposition (PECVD) SiN passivation. A remarkable reduction of the gate leakage current and a significant increase in small signal radio frequency (RF) performance are achieved after applying Al2O3+BCB passivation. For the Al2O3+BCB passivated device with a 0.7 μm gate, the value of fmax reaches up to 100 GHz, but it decreases to 40 GHz for SiN HEMT. The fmax/ft ratio (≥ 4) is also improved after Al2O3+BCB passivation. The capacitance–voltage (C–V) measurement demonstrates that Al2O3+BCB HEMT shows quite less density of trap states (on the order of magnitude of 1010 cm−2) than that obtained at commonly studied SiN HEMT. A GaN high power and efficient amplifier for L-Band Galileo system Giofre, Rocco ; Colantonio, Paolo ; Giannini, Franco ; Gonzalez, Laura ; de Arriba, Francisco ; Cabria, Lorena ; Baglieri, Didier E.E.Dept. University of Roma Tor Vergata, via del Politecnico 1, 00133, Italy Integrated Nonlinear Microwave and Millimetre-wave Circuits Workshop (INMMiC), 2015 http://dx.doi.org/10.1109/INMMIC.2015.7330362

This paper describes the development of an L-Band (f0 = 1.575GHz) high power and efficient amplifier designed for the European satellite navigation system (i.e., Galileo). The amplifier, developed in the framework of the European Project named SLOGAN, exploits the GH50-10 GaN technology available at United Monolithic Semiconductor foundry. The required output power level is achieved by parallelizing several GaN die power bars of 12mm and/or 26.5 mm. In continuous wave operating mode, the first prototype is able to deliver an output power higher than 250W at less than 2 dB of gain compression. Moreover, the registered gain and efficiency are higher than 54 dB and 54 %, respectively. Effect of Reduced Extended Defect Density in MOCVD Grown AlGaN/GaN HEMTs on Native GaN Substrates Anderson, T.J. ; Tadjer, M.J. ; Hite, J.K. ; Greenlee, J.D. ; Koehler, A.D. ; Hobart, K.D. ; Kub, F.J. U.S. Naval Research Laboratory, Washington, DC 20375, USA

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GANEX | Newsletter No. 35 - III-N Technology 19

Electron Device Letters, IEEE http://dx.doi.org/10.1109/LED.2015.2502221

AlGaN/GaN HEMT structures were grown by metal organic chemical vapor deposition (MOCVD) on SiC, hydride vapor phase epitaxy (HVPE) GaN, and ammonothermal GaN substrates to achieve HEMTs with over five orders of magnitude variation in extended defect density. This enables a direct comparision of the effect of extended defects on device performance to achieve the best possible reliability. As-grown material was characterized by atomic force microscopy (AFM), electron channeling contrast imaging (ECCI), and Raman spectroscopy. Devices were characterized by Hall, DC I-V and pulsed I-V behavior. Reduced threading dislocation density provides an increased two-dimensional electron gas (2DEG) mobility, but inhibits ohmic contact formation resulting in high contact resistance. Transistor characteristics were nominally identical, with higher off-state leakage in the HEMTs on ammonothermal GaN. The pulsed I-V response indicated significantly reduced current collapse in the HEMT on HVPE GaN due to reduced buffer trapping. Application Relevant Evaluation of Trapping Effects in AlGaN/GaN HEMTs With Fe-Doped Buffer Axelsson, O. ; Gustafsson, S. ; Hjelmgren, H. ; Rorsman, N. ; Blanck, H. ; Splettstoesser, J. ; Thorpe, J. ; Roedle, T. ; Thorsell, M. Department of Microtechnology and Nanoscience, Chalmers University of Technology, Gothenburg SE-412 96, Sweden Electron Devices, IEEE Transactions on http://dx.doi.org/10.1109/TED.2015.2499313

This paper investigates the impact of different iron (Fe) buffer doping profiles on trapping effects in microwave AlGaN/gallium nitride (GaN) high electron mobility transistors (HEMTs). We characterize not only the current collapse due to trapping in the buffer, but also the recovery process, which is important in the analysis of suitable linearization schemes for amplitude modulated signals. It is shown that the simple pulsed dc measurements of current transients can be used to investigate transient effects in the RF

power. Specifically, it is revealed that the design of the Fe-doping profile in the buffer greatly influences the recovery time, with the samples with lower Fe concentration showing slower recovery. In contrast, traditional indicators, such as S-parameters and dc as well as pulsed $I$-$V$ characteristics, show very small differences. An analysis of the recovery shows that this effect is due to the presence of two different detrapping processes with the same activation energy (0.6 eV) but different time constants. For highly doped buffers, the faster process dominates, whereas the slower process is enhanced for less doped buffers. Gallium nitride power MMICs - promise and problems Campbell, Charles F. ; Qorvo, 500 West Renner Road, Richardson, Texas, 75080, U.S.A Integrated Nonlinear Microwave and Millimetre-wave Circuits Workshop (INMMiC), 2015 http://dx.doi.org/10.1109/INMMIC.2015.7330349

While the advantages of GaN are manifest, many of the features that make GaN transistors attractive can be shown to create significant issues that are typically not encountered with lower voltage technologies. In this talk, specific examples and scenarios are discussed highlighting some selected benefits and issues associated GaN MMIC technology and design. Temperature dependent contact and channel sheet resistance extraction of GaN HEMT Sahoo, A.K. ; Subramani, N.K. ; Nallatamby, J.C. ; Rolland, N. ; Quere, R. ; Medjdoub, F. XLIM Laboratoire, XLIM - UMR CNRS 7250, Université de Limoges, France Integrated Nonlinear Microwave and Millimetre-wave Circuits Workshop (INMMiC), 2015 http://dx.doi.org/10.1109/INMMIC.2015.7330383

In this paper, we carried out a detailed characterization and evaluation of temperature sensitive on-resistance RON (T) of Gallium Nitride (GaN) based High Electron Mobility Transistors (HEMT) through DC and low frequency S-parameters measurements. The measurements

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GANEX | Newsletter No. 35 - III-N Technology 20

are carried out at different chuck temperatures (Tchuck) and the RON (T) is calculated for different values of gate-source bias (VGS) of AlN/GaN/AlGaN HEMT on silicon carbide (SiC) substrate. Knowing RON (T) values for different geometries of the device, we present a practical and simplified method to evaluate the temperature dependent series contact resistance Rse (T) and channel sheet resistance Rsh (T) of the technology. Transistor characterization and modeling and the use of embedding device models for the design of microwave power amplifiers Roblin, Patrick ; Martinez-Rodriguez, Francisco J. ; Hsiu Chen Chang ; Chenggang Xie ; Martinez-Lopez, Jose I. Electrical and Computer Engineering, The Ohio State University, Columbus, 43210, USA Integrated Nonlinear Microwave and Millimetre-wave Circuits Workshop (INMMiC), 2015 http://dx.doi.org/10.1109/INMMIC.2015.7330387

Circuit-based large-signal device models remain extensively used to design integrated and hybrid microwave circuits. It has been recently demonstrated that device models can also be profitably applied under the form of a nonlinear embedding device model to help with the synthesis of multi-transistor power amplifiers (PA) such as Doherty PAs. In this paper we shall discuss this new design process from device modeling to PA design. First an example of an Artificial Neural Network (ANN) SOS-MOSFET model directly extracted from large-signal measurements will be reviewed and its companion ANN nonlinear embedding device model presented. Nonlinear embedding device models can be implemented for other models such as the Angelov model to design PAs. A general methodology for designing two-transistor Doherty or Chireix PAs using an embedding device model will be presented and preliminary simulation results on the design of a GaN Chireix amplifier using an Angelov nonlinear embedding device model will be reported.

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GANEX | Newsletter No. 35 - III-N Technology 21

GROUP 5 - Sensors and MEMS Group leader: Marc Faucher (IEMN) Information selected by Knowmade

A high-overtone bulk acoustic wave resonator-oscillator-based 4.596 GHz frequency source: Application to a coherent population trapping Cs vapor cell atomic clock Thomas Daugey1, Jean-Michel Friedt1, Gilles Martin1 and Rodolphe Boudot1 1 FEMTO-ST, CNRS, UFC, 26 chemin de l’Epitaphe 25030 Besançon Cedex, France Review of Scientific Instruments Vol. 86, 114703 (2015) http://dx.doi.org/10.1063/1.4935172

This article reports on the design and characterization of a high-overtone bulk acoustic wave resonator (HBAR)-oscillator-based 4.596 GHz frequency source. A 2.298 GHz signal, generated by an oscillator constructed around a thermally controlled two-port aluminum nitride-sapphire HBAR resonator with a Q-factor of 24 000 at 68 °C, is frequency multiplied by 2–4.596 GHz, half of the Cs atom clock frequency. The temperature coefficient of frequency of the HBAR is measured to be −23 ppm/ °C at 2.298 GHz. The measured phase noise of the 4.596 GHz source is −105 dB rad2/Hz at 1 kHz offset and −150 dB rad2/Hz at 100 kHz offset. The 4.596 GHz output signal is used as a local oscillator in a laboratory-prototype Cs microcell-based coherent population trapping atomic clock. The signal is stabilized onto the atomic transition frequency by tuning finely a voltage-controlled phase shifter implemented in the 2.298 GHz HBAR-oscillator loop, preventing the need for a high-power-consuming direct digital synthesis. The short-term fractional frequency stability of the free-running oscillator is 1.8 × 10−9 at one second integration time. In locked regime, the latter is improved in a preliminary proof-of-concept experiment at the level of 6.6 × 10−11τ−1/2 up to a few seconds and found to be limited by the signal-to-noise ratio of the detected CPT resonance.

Visible-Blind APD Heterostructure Design With Superior Field Confinement and Low Operating Voltage Bulmer, J. ; Suvarna, P. ; Leathersich, J. ; Marini, J. ; Mahaboob, I. ; Newman, N. ; Shahedipour-Sandvik, F.S. College of Nanoscale Science and Engineering, State University of New York at Albany, Albany, NY, USA Photonics Technology Letters, IEEE Volume:28 , Issue: 1, Page(s):39 - 42 http://dx.doi.org/10.1109/LPT.2015.2479115

We report on the polarization engineering of GaN/AlGaN heterostructures for the improvement of III-Nitride photodetectors through physics-based device simulations. Various heterojunction p-i-n and p-i-n-i-n designs are proposed and analyzed in this context. Our analysis shows that the introduction of a higher-bandgap AlGaN layer and n-type doped composition graded interlayers reduce operating voltage of an avalanche photodetector (APD) by almost 40% while enabling backside illumination geometry that is critical for the realization of detector arrays. The results of the simulation studies predict an APD device design that is less susceptible to premature breakdown outside of the multiplication region due to superior electric field confinement. Acousto-optic modulation of a photonic crystal nanocavity with Lamb waves in microwave K band Semere A. Tadesse1,2, Huan Li1, Qiyu Liu1 and Mo Li1,a) 1 Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA 2 School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA Applied Physics Letters Vol. 107, 201113 (2015) http://dx.doi.org/10.1063/1.4935981

Integrating nanoscale electromechanical transducers and nanophotonic devices potentially

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can enable acousto-optic devices to reach unprecedented high frequencies and modulation efficiency. Here, we demonstrate acousto-optic modulation of a photonic crystal nanocavity using Lamb waves with frequency up to 19 GHz, reaching the microwave K band. The devices are fabricated in suspended aluminum nitride membrane. Excitation of acoustic waves is achieved with interdigital transducers with period as small as 300 nm. Confining both acoustic wave and optical wave within the thickness of the membrane leads to improved acousto-optic modulation efficiency in these devices than that obtained in previous surface acoustic wave devices. Our system demonstrates a scalable optomechanical platform where strong acousto-optic coupling between cavity-confined photons and high frequency traveling phonons can be explored. High spectral response of self-driven GaN-based detectors by controlling the contact barrier height Xiaojuan Sun, Dabing Li, Zhiming Li, Hang Song, Hong Jiang, Yiren Chen, Guoqing Miao & Zhiwei Zhang State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, People’s Republic of China Scientific Reports Vol. 5, Article number: 16819 (2015) http://dx.doi.org/10.1038/srep16819

High spectral response of self-driven GaN-based ultraviolet detectors with interdigitated finger geometries were realized using interdigitated Schottky and near-ohmic contacts. Ni/GaN/Cr, Ni/GaN/Ag, and Ni/GaN/Ti/Al detectors were designed with zero bias responsivities proportional to the Schottky barrier difference between the interdigitated contacts of 0.037 A/W, 0.083 A/W, and 0.104 A/W, respectively. Voltage-dependent photocurrent was studied, showing high gain under forward bias. Differences between the electron and hole mobility model and the hole trapping model were considered to be the main photocurrent gain mechanism. These detectors operate in photoconductive mode with large photocurrent gain and depletion mode with

high speed, and can extend GaN-based metal-semiconductor-metal detector applications. InN-based heterojunction photodetector with extended infrared response Lung-Hsing Hsu,1 Chien-Ting Kuo,1 Jhih-Kai Huang,2 Shun-Chieh Hsu,3 Hsin-Ying Lee,4 Hao-Chung Kuo,2 Po-Tsung Lee,2 Yu-Lin Tsai,2 Yi-Chia Hwang,3 Chen-Feng Su,3 Jr-Hau He,5 Shih-Yen Lin,6 Yuh-Jen Cheng,6 and Chien-Chung Lin3,* 1Institute of Lighting and Energy Photonics, National Chiao Tung University, Tainan 71150, Taiwan 2Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan 3Institute of Photonic System, National Chiao Tung University, Tainan 71150, Taiwan 4Department of Photonics, National Cheng Kung University, Tainan 70101, Taiwan 5Computer, Electrical and Mathematical Sciences and Engineering (CEMSE) Division, King Abdullah University of Science & Technology (KAUST), Thuwal 23955-6900, Saudi Arabia 6Research Center for Applied Sciences, Academia Sinica, Taiwan Optics Express Vol. 23, Issue 24, pp. 31150-31162 (2015) http://dx.doi.org/10.1364/OE.23.031150

The combination of ZnO, InN, and GaN epitaxial layers is explored to provide long wavelength photodetection capability in the GaN based materials. Growth temperature optimization was performed to obtain the best quality of InN epitaxial layer in the MOCVD system. The temperature dependent photoluminescence (PL) can provide the information about thermal quenching in the InN PL transitions and at least two non-radiative processes can be observed. X-ray diffraction and energy dispersive spectroscopy are applied to confirm the inclusion of indium and the formation of InN layer. The band alignment of such system shows a typical double heterojunction, which is preferred in optoelectronic device operation. The photodetector manufactured by this ZnO/GaN/InN layer can exhibit extended long-wavelength quantum efficiency, as high as 3.55%, and very strong photocurrent response under solar simulator illumination.

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Chipscale GHz ultrasonic channels for fingerprint scanning Hoople, J. ; Kuo, J. ; Abdel-moneum, Mohamed ; Lal, A. SonicMEMS Laboratory, School of Electrical and Computer Engineering, USA Ultrasonics Symposium (IUS), 2015 IEEE International http://dx.doi.org/10.1109/ULTSYM.2015.0027

In this paper we present 1–3 GHz frequency ultrasonic interrogation of surface ultrasonic impedances. The chipscale and CMOS integration of GHz transducers can enable surface identification imaging for many applications. We use aluminum nitride piezoelectric thin films driven at maximum amplitudes of 4-Vpp to launch and measure pulse packets. In this paper we first use the contrast in ultrasonic impedance between air and skin to create an image of a fingerprint. As a second application we directly measure the reflection coefficient for different liquids to demonstrate the ability to measure the ultrasonic impedance and distinguish between three different liquids. Using a rubber phantom the image of a portion of a fingerprint is captured by measuring changes in signal levels at the resonance frequency of the piezoelectric transducers 2.7 GHz. Reflected amplitude waves from air and skin differ by factors of 1.8–2. The measurements for three different liquids; water, isopropyl alcohol, and acetone show that the three liquids have sufficiently different acoustic impedances to be able to identify them. High-Q piezoelectric Lamb wave resonators based on AlN plates with chamfered corners Lin, Chih-Ming ; Zou, Jie ; Chen, Yung-Yu ; Pisano, Albert P. Department of Mechanical Engineering, University of California, Berkeley, 94720, USA Ultrasonics Symposium (IUS), 2015 IEEE International http://dx.doi.org/10.1109/ULTSYM.2015.0360

A novel approach to the boost quality factor (Q) of Lamb wave resonators by chamfering the aluminum nitride (AlN) plate is investigated for the first time. It is well-known that the Q's of the AlN Lamb wave resonators are degraded due to energy dissipation through the support tethers. In

this work, similar to the beveled edges used in AT-cut quartz resonators, the chamfered corners are utilized to trap vibration energy in the AlN plate to enhance the anchor Q's. Based on finite element analysis (FEA) simulated results, the AlN plate with chamfered corners can efficiently reduce mechanical vibrations in support tethers and trap more mechanical energy in the plate. The experimental results demonstrate that the loaded Q of the Lamb wave resonator is boosted from 2,041 to 3,016 and the minimum impedance is reduced from 87.4 O to 61.6 O by simply chamfering the AlN rectangular plate, showing a 1.48× increase in measured Q's. Temperature compensation of the AlN Lamb wave resonators utilizing the S1 mode Zou, Jie ; Pisano, Albert P. University of California, Berkeley, 94720, USA Ultrasonics Symposium (IUS), 2015 IEEE International http://dx.doi.org/10.1109/ULTSYM.2015.0456

The temperature compensation techniques for the first-order symmetric (S1) Lamb wave mode in the AlN Lamb wave resonators are firstly investigated in this paper. The S1 mode simultaneously offers very high phase velocity (νp) and large coupling coefficient (k2) when hAlN/λ is smaller than 0.4, but its thermal stability needs further improvement. The AlN/SiO2 bilayer and SiO2/AlN/SiO2 sandwiched temperature compensation structures are investigated and compared in this study. The SiO2/AlN/SiO2 symmetric structure shows higher vp and larger k2 than the lowest-order quasi-symmetric (QS1) mode traveling in the AlN/SiO2 bilayer structure because the symmetric structure trapes more acoustic energy inside the AlN piezoelectric layer. Despite the trade-off between first-order temperature coefficient of frequency (TCF) and k2, the SiO2/AlN/SiO2 structure can provide large k2 and near-zero TCF at the same time with proper thickness selection of AlN and SiO2. The temperature-compensated resonator utilizing the S1 mode in the symmetrical SiO2/AlN/SiO2 sandwiched membrane can simultaneously offer excellent thermal compensation, and large k2 at super-high frequency.

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GROUP 6 - Photovoltaics and Energy harvesting Group leader: Eva Monroy (INAC-CEA)

Information selected by Knowmade

Influence of the ITO current spreading layer on efficiencies of InGaN-based solar cells J. Bai, M. Athanasiou, T. Wang Department of Electronics and Electrical Engineering, University of Sheffield, Sheffield S1 3JD, United Kingdom Solar Energy Materials and Solar Cells http://dx.doi.org/10.1016/j.solmat.2015.10.026

A systematic investigation of the utilization of indium-tin-oxide (ITO) as a current spreading layer (CSL) with and without a textured surface has been performed on InGaN-based solar cells, demonstrating a difference in the influence on the performance of the devices. It is found that employing an ITO CSL improves the conversion efficiency for devices with planar surfaces; whereas it reduces the efficiency for the surface textured devices. Consequently, best performance is achieved for the surface-textured solar cell without employing an ITO CSL, with an enhancement of 75% in the conversion efficiency compared to the planar cell without ITO. Our reflectance measurements show that the ITO CSL can effectively suppress surface reflection for the planar devices, while it becomes less effective for the surface-textured devices. Furthermore, a transmission measurement is carried out to estimate the absorption of the ITO CSL. The influence of the ITO CSL is discussed in terms of surface reflection and light loss due to the ITO shading effect as well as power loss associated with the absence of the ITO CSL. Application of GaN for photoelectrolysis of water M V Puzyk1, A S Usikov2,3, S Yu Kurin4, A M Puzyk1, A D Fomichev2, I A Ermakov2, D S Kovalev2, B P Papchenko2, H Helava3 and Yu N Makarov3,4 Herzen University, Nab. r. Moyki 48, St. Petersburg 194186, Russia 2 University ITMO, Kronverkskiy pr. 49, St. Petersburg 197101, Russia 3 Nitride Crystals Inc., 181 E Industry Court, Suite B, Deer Park, NY 11729, USA 4 Nitride Crystals Group, Ltd., pr. Engel'sa 27, St. Petersburg 194156, Russia

Journal of Physics: Conference Series http://dx.doi.org/10.1088/1742-6596/643/1/012127

GaN layers of n-type and p-type conductivity grown by HVPE on sapphire substrates were used as working electrodes for water electrolysis, photoelectrolysis and hydrogen gas generation. Specifically the water splitting process is discussed. Corrosion of the GaN materials is also considered. The hydrogen production rate under 365-nm UV LED irradiation of the GaN and external bias was 0.3 ml/(cm2*h) for an n-GaN photoanode (n~8×1016 cm-3) in 1M Na2SO4 electrolyte and 1.2 ml/(cm2*h) for an n-GaN photoanode (n~1×1017 cm-3) in 1M KOH electrolyte. Modeling, synthesis and study of highly efficient solar cells based on III-nitride nanowire arrays grown on Si substrates A M Mozharov1, A D Bolshakov1, D A Kudryashov1, N V Kryzhanovskaya1, G E Cirlin1, I S Mukhin1,2, J C Harmand3 and M Tchernysheva3 1 St.Petersburg Academic University, Khlopina 8/3, 194021, St. Petersburg, Russia 2 ITMO University, Kronverkskij 49, 197101, St. Petersburg, Russia 3 CNRS-LPN, Route de Nozay, Marcoussis, 91460 France Journal of Physics: Conference Series http://dx.doi.org/10.1088/1742-6596/643/1/012115

In this letter we investigate photovoltaic properties of GaN nanowires (NWs) – Si substrate heterostructure obtained by molecular beam epitaxy (MBE). Antireflection properties of the NW array were studied theoretically and experimentally to show an order of magnitude enhancement in antireflection comparing to the pure Si surface (2.5% vs. 33.8%). In order to determine optimal morphology and doping levels of the structure with maximum possible efficiency we simulated it's properties using a finite difference method. The carried out simulation showed that a maximum efficiency should be 20%.

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GROUP 7 - Materials, Technology and Fundamental Group leader: Jean-Christophe Harmand (LPN-CNRS)

NANO

Information selected by Knowmade

Enhanced Raman scattering and weak localization in graphene deposited on GaN nanowires Jakub Kierdaszuk1,*, Piotr Kaźmierczak1, Aneta Drabińska1, Krzysztof Korona1, Agnieszka Wołoś1,2, Maria Kamińska1, Andrzej Wysmołek1, Iwona Pasternak3, Aleksandra Krajewska3,4, Krzysztof Pakuła1, and Zbigniew R. Zytkiewicz2 1Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02–093, Warsaw, Poland 2Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02–668, Warsaw, Poland 3Institute of Electronic Materials Technology, ul. Wólczyńska 133, 01–919, Warsaw, Poland 4Institute of Optoelectronics, Military University of Technology, ul. Gen. Sylwestra Kaliskiego 2, 01–476, Warsaw, Poland Physical Review B Vol. 92, 195403 http://dx.doi.org/10.1103/PhysRevB.92.195403

The influence of GaN nanowires on the optical and electrical properties of graphene deposited on them was studied using Raman spectroscopy and a microwave-induced electron transport method. It was found that the interaction with the nanowires induces spectral changes and leads to a significant enhancement of the Raman scattering intensity. Surprisingly, the smallest enhancement (about 30-fold) was observed for the defect induced D′ process, and the highest intensity increase (over 50-fold) was found for the 2D transition. The observed energy shifts of the G and 2D bands allowed us to determine the carrier concentration fluctuations induced by the GaN nanowires. A comparison of the Raman scattering spatial intensity maps and the images obtained using a scanning electron microscope led to a conclusion that the vertically aligned GaN nanowires induce a homogenous strain, substantial spatial modulation of the carrier concentration in graphene, and unexpected homogenous distribution of defects created by

the interaction with the nanowires. The analysis of the D and D′ peak intensity ratio showed that the interaction with the nanowires also changes the probability of scattering on different types of defects. The Raman studies were correlated with the weak localization effect measured using microwave-induced contactless electron transport. The temperature dependence of the weak localization signal showed electron-electron scattering as the main decoherence mechanism with an additional, temperature-independent scattering-reducing coherence length. We attributed it to the interaction of electrons in graphene with charges present on top of nanowires due to the spontaneous and piezoelectric polarization of GaN. Thus, nanowires act as antennas and generate an enhanced near field, which can explain the observed significant enhancement of the Raman scattering intensity. Improved control over spontaneously formed GaN nanowires in molecular beam epitaxy using a two-step growth process J K Zettler, P Corfdir, L Geelhaar, H Riechert, O Brandt and S Fernández-Garrido Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5–7, D-10117 Berlin, Germany Nanotechnology Vol. 26; 445604 http://dx.doi.org/10.1088/0957-4484/26/44/445604

We investigate the influence of modified growth conditions during the spontaneous formation of GaN nanowires (NWs) on Si(111) in plasma-assisted molecular beam epitaxy. We find that a two-step growth approach, where the substrate temperature is increased during the nucleation stage, is an efficient method to gain control over the area coverage, average diameter, and coalescence degree of GaN NW ensembles. Furthermore, we also demonstrate that the growth conditions employed during the incubation time that precedes nanowire nucleation do not influence the properties of the final nanowire ensemble. Therefore, when growing GaN NWs at elevated temperatures or

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with low Ga/N ratios, the total growth time can be reduced significantly by using more favorable growth conditions for nanowire nucleation during the incubation time. GaN and GaxIn1−xN Nanoparticles with Tunable Indium Content: Synthesis and Characterization Dr. WeiWei Lei, Dr. Marc Georg Willinger, Prof. Markus Antonietti, Dr. Cristina Giordano Department of Colloid Chemistry Max Planck Institute of Colloids and Interfaces Research Campus Golm, 14424 Potsdam Department of Inorganic Chemistry Fritz Haber Insti tute of the Max Planck Society Faradayweg 4-6, 14195 Berlin Institute for Frontier Materials, Deakin University Waurn Ponds VIC 3217 School of Biological and Chemical Sciences Queen Mary University of London, Mile End Road London E1 4NS Chemistry A European Journal 2015, 21,1–8 http://dx.doi.org/10.1002/chem.201502875

Semiconducting GaN and GaxIn1−xN nanoparticles (4–10 nm in diameter, depending on the metal ratio) with tunable indium content are prepared through a chemical synthesis (the urea-glass route). The bandgap of the ternary system depends on its composition, and therefore, the color of the final material can be turned from bright yellow (the color of pure GaN) to blue (the color of pure InN). Transmission electron microscopy (TEM and HRTEM) and scanning electron microscopy (SEM) images confirm the nanoparticle character and homogeneity of the as-prepared samples. X-ray diffraction (XRD), electron diffraction (EDX), elemental mapping, and UV/Vis, IR, and Raman spectroscopy investigations are used to confirm the incorporation of indium into the crystal structure of GaN. These nanoparticles, possessing adjusted optical properties, are expected to have potential applications in the fabrication of novel optoelectronic devices. Nanostructures of Indium Gallium Nitride Crystals Grown on Carbon Nanotubes Ji-Yeon Park, Keun Man Song & Sung-Nam Lee, Keun Man Song, Yo-Sep Min, Chel-Jong Choi, Yoon Seok Kim Department of Nano-Otpical Engineering, Korea Polytechnic University, Siheung, Gyeonggi 429-793

Republic of Korea; Department of Chemical Engineering, Konkuk University, Seoul 143-701 Republic of Korea; Korea Advanced Nano Fab Center, Suwon, Gyeonggi ; Photonics Device Research Center, Korea Photonics Technology Institute (KOPTI), Gwangju 500-460 Republic of KoreaSchool of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center, Chonbuk National University, Jeonju, Chonbuk 561-756 Republic of Korea443-770 Republic of Korea Scientific Reports Vol. 5, Article number: 16612 (2015) http://dx.doi.org/10.1038/srep16612

Nanostructure (NS) InGaN crystals were grown on carbon nanotubes (CNTs) using metalorganic chemical vapor deposition. The NS-InGaN crystals, grown on a ~5-μm-long CNT/Si template, were estimated to be ~100–270 nm in size. Transmission electron microscope examinations revealed that single-crystalline InGaN NSs were formed with different crystal facets. The observed green (~500 nm) cathodoluminescence (CL) emission was consistent with the surface image of the NS-InGaN crystallites, indicating excellent optical properties of the InGaN NSs on CNTs. Moreover, the CL spectrum of InGaN NSs showed a broad emission band from 490 to 600 nm. Based on these results, we believe that InGaN NSs grown on CNTs could aid in overcoming the green gap in LED technologies. Vertically aligned InGaN nanowires with engineered axial In composition for highly efficient visible light emission Mohamed Ebaid, Jin-Ho Kang, Yang-Seok Yoo, Seung-Hyuk Lim, Yong-Hoon Cho & Sang-Wan Ryu Department of Physics, Chonnam National University, Gwangju 500-757, Republic of Korea Department of Physics and KI for the NanoCentury, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Republic of Korea Department of Physics, Faculty of Science, Beni-Suef University, Beni-Suef 62511, Egypt Scientific Reports Vol. 5, Article number: 17003 (2015) http://dx.doi.org/10.1038/srep17003

We report on the fabrication of novel InGaN nanowires (NWs) with improved crystalline quality

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and high radiative efficiency for applications as nanoscale visible light emitters. Pristine InGaN NWs grown under a uniform In/Ga molar flow ratio (UIF) exhibited multi-peak white-like emission and a high density of dislocation-like defects. A phase separation and broad emission with non-uniform luminescent clusters were also observed for a single UIF NW investigated by spatially resolved cathodoluminescence. Hence, we proposed a simple approach based on engineering the axial In content by increasing the In/Ga molar flow ratio at the end of NW growth. This new approach yielded samples with a high luminescence intensity, a narrow emission spectrum, and enhanced crystalline quality. Using time-resolved photoluminescence spectroscopy, the UIF NWs exhibited a long radiative recombination time (τr) and low internal quantum efficiency (IQE) due to strong exciton localization and carrier trapping in defect states. In contrast, NWs with engineered In content demonstrated three times higher IQE and a much shorter τr due to mitigated In fluctuation and improved crystal quality.

NON/SEMI POLAR Information selected by

Philippe De Mierry (CRHEA-CNRS) The determining factor of a preferred orientation of GaN domains grown on m-plane sapphire substrates Cheol-Woon Kim, Seoung-Hun Kang, Hansub Yoon, Dongsoo Jang, Young-Kyun Kwon & Chinkyo Kim Department of Physics and Research Institute for Basic Sciences, Kyung Hee University, 26 Kyungheedae-ro, Dongdaemun-gu, Seoul 02447, Korea Miyeon Jue Scientific Reports

Vol. 5, Article number: 16236 (2015)

http://dx.doi.org/10.1038/srep16236

Epitaxial lateral overgrowth in tandem with the first-principles calculation was employed to investigate the determining factor of a preferred orientation of GaN on SiO2-patterned m-plane sapphire substrates. We found that the (100)-orientation is favored over the (10)-orientation in

the region with a small filling factor of SiO2, while the latter orientation becomes preferred in the region with a large filling factor. This result suggests that the effective concentration determines the preferred orientation of GaN: the (100)- and (10)-orientations preferred at their low and high concentrations, respectively. Our computational study revealed that at a low coverage of Ga and N atoms, the local atomic arrangement resembles that on the (10) surface, although the (100) surface is more stable at their full coverage. Such a (10)-like atomic configuration crosses over to the local structure resembling that on the (100) surface as the coverage increases. Based on results, we determined that high effective concentration of Ga and N sources expedites the growth of the (10)-orientation while keeping from transition to the (100)-orientation. At low effective concentration, on the other hand, there is a sufficient time for the added Ga and N sources to rearrange the initial (10)-like orientation to form the (100)-orientation.

Nonpolar m-plane GaN/AlGaN heterostructures with intersubband transitions in the 5–10 THz band C B Lim1,2, A Ajay1,2, C Bougerol1,3, B Haas1,2, J Schörmann4, M Beeler1,2, J Lähnemann1,2, M Eickhoff4 and E Monroy1,2 1 University Grenoble-Alpes, F-38000 Grenoble, France 2 CEA, INAC-SP2M, 17 av. des Martyrs, F-38000 Grenoble, France 3 CNRS, Institut Néel, 25 av. des Martyrs, F-38000 Grenoble, France 4 I. Physikalisches Institut, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 16, D-35392 Gießen, Germany Nanotechnology

Vol. 26; 435201

http://dx.doi.org/10.1088/0957-4484/26/43/435201

This paper assesses intersubband (ISB) transitions in the 1–10 THz frequency range in nonpolar m-plane GaN/AlGaN multi-quantum-wells deposited on free-standing semi-insulating GaN substrates. The quantum wells (QWs) were designed to contain two confined electronic levels, decoupled from the neighboring wells. Structural analysis reveals flat and regular QWs in the two

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perpendicular in-plane directions, with high-angle annular dark-field scanning transmission electron microscopy images showing inhomogeneities of the Al composition in the barriers along the growth axis. We do not observe extended structural defects (stacking faults or dislocations) introduced by the epitaxial process. Low-temperature ISB absorption from 1.5 to 9 THz (6.3–37.4 meV) is demonstrated, covering most of the 7–10 THz band forbidden to GaAs-based technologies.

TEM investigation of semipolar GaN layers grown on Si(001) offcut substrates L M Sorokin1, A V Myasoedov1, A E Kalmykov1, D A Kirilenko1,2, V N Bessolov1 and S A Kukushkin3 1 Ioffe Institute, 26 Polytekhnicheskaya, St. Petersburg, 194021, Russia 2 NBIC Centre, NRC Kurchatov Institute, Moscow, 123182, Russia 3 Institute for Problems of Mechanical Engineering, Russian Academy of Sciences, V.O., Bolshoy pr. 61, St. Petersburg, 199178, Russia Semiconductor Science and Technology

Vol. 30; 114002

http://dx.doi.org/10.1088/0268-1242/30/11/114002

We present the results of a conventional and high-resolution electron microscopy investigation of thick (up to 15 μm) semipolar GaN layers grown on Si(001) offcut substrates with 3C-SiC and AlN buffer layers. GaN and AlN layers have been grown by chloride vapor phase epitaxy. The silicon carbide buffer layers were produced by a new method of solid-phase synthesis on 4 and 7° offcut Si(001) substrates. It is shown that the use of solid-phase synthesis for the formation of SiC layer allows one to grow a semipolar GaN layer. The asymmetrical defect structure of the semipolar layer is revealed.

Polar and semipolar (112‾2) InAlN layers grown on AlN templates using MOVPE Duc V. Dinh1,*, Haoning Li1,2 and Peter J. Parbrook1,2

1Tyndall National Institute, University College Cork, Lee Maltings, Dyke Parade, Cork, Ireland 2School of Engineering, University College Cork, Cork, Ireland

Physica status solidi (b)

http://dx.doi.org/10.1002/pssb.201552264

We report on metalorganic vapor phase epitaxial growth of InAlN layers on (0001) and (11inline image2) AlN templates at different temperatures (725–800 °C). The indium content (8.0–15.2%) of the (11inline image2) InAlN layers was found to be lower compared to that for the (0001) layers (9.0–23.0%). The higher indium content of the (0001) layers was attributed to a high density of small hillocks and a larger degree of relaxation. The small hillocks on the (0001) layer surface acted as quantum-dot-like structures that caused a stronger emission at longer wavelength compared to weaker emission at shorter wavelength from a “bulk” layer underneath. A large Stokes-shift of about 300 and 480 meV was observed for the (0001) and (inline image) layers, respectively. The larger shift of the (11inline image2) layers was attributed to a higher degree of localization. The larger degree of localization and higher unintentional oxygen incorporation enhanced the luminescence intensity of the (11inline image2) layers compared to that for the (0001) layers. Green emission from semipolar InGaN quantum wells grown on low-defect (112¯2) GaN templates fabricated on patterned r-sapphire P. de Mierry*, L. Kappei, F. Tendille, P. Vennéguès, M. Leroux and J. Zuniga-Perez CNRS-CRHEA, Valbonne, France Physica status solidi (b)

http://dx.doi.org/10.1002/pssb.201552298

In this article, InGaN/GaN multiple quantum wells (MQWs) grown on low-defect (inline image) GaN templates are investigated by photoluminescence (PL), cathodoluminescence (CL), and transmission electron microscopy (TEM). The emission wavelength is tuned from 450 nm (blue) to 550 nm (green) by varying the TMGa flux in the QWs, while keeping the temperature constant. The In content in the QWs is found to increase with increasing TMGa flux. CL measurements show that the first QW and often the second one emit systematically at wavelengths shorter than the following QWs, while TEM measurements

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indicate that these first QWs are slightly thinner and display less In content than the rest of the stack. Both observations might be explained by considering that these first QWs grow under larger compressive strain than the subsequent QWs. Furthermore, since TEM shows that misfit dislocations oriented along the [inline image] direction are mainly located at the lower MQW stack interface, i.e., between the first QW and the underlying template, the correlation between TEM and CL points toward a plastic relaxation occurring after the stacking of a sufficiently large number of QWs. Direct microscopic correlation of real structure and optical properties of semipolar GaN based on pre-patterned r-plane sapphire Sebastian Metzner1,*, Frank Bertram1, Thomas Hempel1, Tobias Meisch2, Stephan Schwaiger2, Ferdinand Scholz2 and Jürgen Christen1 1Institute of Experimental Physics, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany 2Institute of Optoelectronics, University of Ulm, Ulm, Germany Physica status solidi (b)

http://dx.doi.org/10.1002/pssb.201552467

Spatially resolved cathodoluminescence (CL) microscopy is used to study semipolar inline image gallium nitride (GaN) grown out of trenches with c-plane-like sidewalls etched into the r-plane inline image sapphire substrate. The beneficial effect of growing locally c-GaN on c-sapphire and subsequent switching to the semipolar growth mode manifests in bending of threading dislocations (TDs) and a +c-wing of excellent material properties represented by pure donor-bound-exciton emission. The − c-wing, on the other hand, is strongly affected by a huge number of stacking faults and other structural defects. An optimized growth process leads to a delayed coalescence of the single GaN stripes which allows to block the complete − c-wing including all the defects by a void, and coalescence occurs only between the +c-wings consisting of GaN with excellent material quality. The final semipolar inline image GaN surface shows exclusively CL of the donor-bound exciton (D0, X) recombination and no other spectral contribution of structural

defects and a reduced TD density. After coalescence and further growth a significant increase of the homogeneity of the CL intensity and emission wavelength is observed for thick samples. CL of an InGaN/GaN active region deposited on top reveals homogeneous luminescence properties over the coalesced region showing no modulation related to the pre-structured growth mode as the defect containing growth domains are effectively blocked.

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Agnès Trassoudaine (Université d'Auvergne) and Yvon Cordier (CRHEA-CNRS)

Screw dislocation-induced growth spirals as emissive exciton localization centers in Al-rich AlGaN/AlN quantum wells Mitsuru Funato1,a), Ryan G. Banal1,b) and Yoichi Kawakami1 1 Department of Electronic Science and Engineering, Kyoto University, Kyoto 615-8510, Japan AIP Advances

Vol. 5, 117115 (2015)

http://dx.doi.org/10.1063/1.4935567

Screw dislocations in Al-rich AlGaN/AlN quantum wells cause growth spirals with an enhanced Ga incorporation, which create potential minima. Although screw dislocations and their surrounding potential minima suggest non-radiative recombination processes within growth spirals, in reality, screw dislocations are not major non-radiative sinks for carriers. Consequently, carriers localized within growth spirals recombine radiatively without being captured by non-radiative recombination centers, resulting in intense emissions from growth spirals.

Dislocation-assisted tunnelling of charge carriers across the Schottky barrier on the hydride vapour phase epitaxy grown GaN Abhishek Chatterjee1,a), Shailesh K. Khamari1, V. K. Dixit1, S. M. Oak1 and T. K. Sharma1,b) 1 Semiconductor Physics and Devices Laboratory, Raja Ramanna Centre for Advanced Technology, Indore-452013, India

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GANEX | Newsletter No. 35 - III-N Technology 30

Journal of Applied Physics

Vol. 118, 175703 (2015)

http://dx.doi.org/10.1063/1.4934862

Barrier height and Ideality factor of Ni/n-GaN Schottky diodes are measured by performing temperature dependent current-voltage measurements. The measured value of barrier height is found to be much smaller than the theoretically calculated Schottky-Mott barrier height for the Ni/n-GaN diodes. Furthermore, a high value of ideality factor (>2) is measured at low temperatures. In order to understand these results, we need to consider a double Gaussian distribution of barrier height where the two components are related to the thermionic emission and thermionic filed emission mediated by dislocation-assisted tunnelling of carriers across the Schottky barrier. Thermionic emission is seen to dominate at temperatures higher than 170 K while the dislocation-assisted tunnelling dominates at low temperatures. The value of characteristic tunnelling energy measured from the forward bias current-voltage curves also confirms the dominance of dislocation-assisted tunnelling at low temperatures which is strongly corroborated by the Hall measurements. However, the value of characteristic tunnelling energy for high temperature range cannot be supported by the Hall results. This discrepancy can be eliminated by invoking a two layer model to analyse the Hall data which confirms that the charged dislocations, which reach the sample surface from the layer-substrate interface, provide an alternate path for the transport of carriers. The dislocation-assisted tunnelling of carriers governs the values of Schottky diode parameters at low temperature and the same is responsible for the observed inhomogeneity in the values of barrier height. The present analysis is applicable wherever the charge transport characteristics are severely affected by the presence of a degenerate layer at GaN-Sapphire interface and dislocations lines pierce the Schottky junction to facilitate the tunnelling of carriers.

Spotting 2D atomic layers on aluminum nitride thin films Hareesh Chandrasekar, Krishna Bharadwaj B, Kranthi Kumar Vaidyuala, Swathi Suran, Navakanta Bhat, Manoj

Varma and Srinivasan Raghavan

Centre for Nano Science and Technology, Indian Institute of Science, CV Raman Road, Bangalore 560012, India Nanotechnology

Vol. 26; 425202

http://dx.doi.org/10.1088/0957-4484/26/42/425202

Substrates for 2D materials are important for tailoring their fundamental properties and realizing device applications. Aluminum nitride (AIN) films on silicon are promising large-area substrates for such devices in view of their high surface phonon energies and reasonably large dielectric constants. In this paper epitaxial layers of AlN on 2'' Si wafers have been investigated as a necessary first step to realize devices from exfoliated or transferred atomic layers. Significant thickness dependent contrast enhancements are both predicted and observed for monolayers of graphene and MoS2 on AlN films as compared to the conventional SiO2 films on silicon, with calculated contrast values approaching 100% for graphene on AlN as compared to 8% for SiO2 at normal incidences. Quantitative estimates of experimentally measured contrast using reflectance spectroscopy show very good agreement with calculated values. Transistors of monolayer graphene on AlN films are demonstrated, indicating the feasibility of complete device fabrication on the identified layers.

Relationship between misfit-dislocation formation and initial threading-dislocation density in GaInN/GaN heterostructures Motoaki Iwaya1, Taiji Yamamoto1, Daisuke Iida1, Yasunari Kondo1, Mihoko Sowa1, Hiroyuki Matsubara1, Koji Ishihara1, Tetsuya Takeuchi1, Satoshi Kamiyama1 and Isamu Akasaki1,2 1 Faculty of Science and Technology, Meijo University, Nagoya 468-8502, Japan 2 Akasaki Research Center, Nagoya University, Nagoya 464-8603, Japan Japanese Journal of Applied Physics

Vol. 54; 115501

http://dx.doi.org/10.7567/JJAP.54.115501

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The dependence of the critical thickness for the introduction of misfit dislocations in a GaInN/GaN heterostructure system on the dislocation density in the underlying GaN layer was investigated using in situ X-ray diffraction (XRD), ex situ scanning electron microscopy, and transmission electron microscopy analyses. The critical thickness for the introduction of misfit dislocations in the GaInN layer was found to significantly depend on the dislocation density in the underlying GaN layer. Notably, on the basis of the in situ XRD results, a reliable critical thickness for obtaining misfit-dislocation-free growth was determined.

Elimination of surface band bending on N-polar InN with thin GaN capping J. Kuzmík1,a), Š. Haščík1, M. Kučera1, R. Kúdela1, E. Dobročka1, A. Adikimenakis2, M. Mičušík3, M. Gregor4, A. Plecenik4 and A. Georgakilas5 1 Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravska cesta 9, 841 04 Bratislava, Slovakia 2 Microelectronics Research Group (MRG), IESL, FORTH, P.O. Box 1385, 71110 Heraklion, Crete, Greece 3 Polymer Institute, Slovak Academy of Sciences, Dúbravska cesta 9, 845 41 Bratislava, Slovakia 4 Faculty of Mathematics, Physics and Informatics, Comenius University in Bratislava, Mlynská dolina, 842 48 Bratislava, Slovakia 5 Microelectronics Research Group (MRG), IESL, FORTH, P.O. Box 1385, 71110 Heraklion, Greece and Department of Physics, University of Crete, 71203 Heraklion, Greece Applied Physics Letters

Vol. 107, 191605 (2015)

http://dx.doi.org/10.1063/1.4935615

0.5–1 μm thick InN {0001} films grown by molecular-beam epitaxy with N- or In-polarity are investigated for the presence of native oxide, surface energy band bending, and effects introduced by 2 to 4 monolayers of GaN capping. Ex situ angle-resolved x-ray photo-electron spectroscopy is used to construct near-surface (GaN)/InN energy profiles, which is combined with deconvolution of In3d signal to trace the presence of InN native oxide for different types of polarity and capping. Downwards surface energy band bending was observed on bare samples with native oxide, regardless of the polarity. It was found that the In-polar InN surface is most readily

oxidized, however, with only slightly less band bending if compared with the N-polar sample. On the other hand, InN surface oxidation was effectively mitigated by GaN capping. Still, as confirmed by ultra-violet photo-electron spectroscopy and by energy band diagram calculations, thin GaN cap layer may provide negative piezoelectric polarization charge at the GaN/InN hetero-interface of the N-polar sample, in addition to the passivation effect. These effects raised the band diagram up by about 0.65 eV, reaching a flat-band profile.

Carrier and photon dynamics in a topological insulator Bi2Te3/GaN type II staggered heterostructure P. Chaturvedi1, S. Chouksey1, D. Banerjee1, S. Ganguly1 and D. Saha1,a) 1 Applied Quantum Mechanics Laboratory, Centre of Excellence in Nanoelectronics, Department of Electrical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India Applied Physics Letters

Vol. 107, 192105 (2015)

http://dx.doi.org/10.1063/1.4935554

We have demonstrated a type-II band-aligned heterostructure between pulsed laser deposited topological insulator bismuth telluride and metal organic-chemical-vapour deposited GaN on a sapphire substrate. The heterostructure shows a large valence band-offset of 3.27 eV as determined from x-ray photoelectron spectroscopy, which is close to the bandgap of GaN (3.4 eV). Further investigation using x-ray diffraction, Raman spectroscopy, and energy-dispersive x-ray spectrum reveals the stoichiometric and material properties of bismuth telluride on GaN. Steady state photon emission from GaN is found to be modulated by the charge transfer process due to diffusion across the junction. The time constant involved with the charge transfer process is found to be 0.6 ns by transient absorption spectroscopy. The heterostructure can be used for designing devices with different functionalities and improving the performance of the existing devices on GaN.

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GANEX | Newsletter No. 35 - III-N Technology 32

Microstructures and growth mechanisms of GaN films epitaxially grown on AlN/Si hetero-structures by pulsed laser deposition at different temperatures Wenliang Wang1, Weijia Yang1, Yunhao Lin1, Shizhong Zhou1 & Guoqiang Li1,2 1State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China. 2Engineering Research Center on Solid-State Lighting and its Informationisation of Guangdong Province, Guangzhou 510640, China. Scientific Reports

Vol. 5, Article number: 16453 (2015)

http://dx.doi.org/10.1038/srep16453

2 inch-diameter GaN films with homogeneous thickness distribution have been grown on AlN/Si(111) hetero-structures by pulsed laser deposition (PLD) with laser rastering technique. The surface morphology, crystalline quality, and interfacial property of as-grown GaN films are characterized in detail. By optimizing the laser rastering program, the ~300 nm-thick GaN films grown at 750 °C show a root-mean-square (RMS) thickness inhomogeneity of 3.0%, very smooth surface with a RMS surface roughness of 3.0 nm, full-width at half-maximums (FWHMs) for GaN(0002) and GaN(102) X-ray rocking curves of 0.7° and 0.8°, respectively, and sharp and abrupt AlN/GaN hetero-interfaces. With the increase in the growth temperature from 550 to 850 °C, the surface morphology, crystalline quality, and interfacial property of as-grown ~300 nm-thick GaN films are gradually improved at first and then decreased. Based on the characterizations, the corresponding growth mechanisms of GaN films grown on AlN/Si hetero-structures by PLD with various growth temperatures are hence proposed. This work would be beneficial to understanding the further insight of the GaN films grown on Si(111) substrates by PLD for the application of GaN-based devices.

GaN heterostructures with diamond and graphene B Pécz1, L Tóth1, G Tsiakatouras2, A Adikimenakis2, A Kovács3, M Duchamp3, R E Dunin-Borkowski3, R Yakimova4, P L Neumann1, H Behmenburg5, B Foltynski5, C Giesen5, M Heuken5 and A Georgakilas2

1 Institute for Technical Physics and Materials Science, Centre for Energy Research, Hungarian Academy of Sciences, MTA EK MFA, 1121 Budapest, Konkoly-Thege M. u. 29-33, Hungary 2 IESL/FORTH and Physics Department/University Crete, P. O. Box 1385, 71110 Heraklion, Greece 3 Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Peter Grünberg Institute, Forschungszentrum Jülich, D-52425, Germany 4 Department of Physics, Chemistry and Biology, Linköping University, S-581 83 Linköping, Sweden 5 AIXTRON SE, Kaiserstrasse 98, 52134 Herzogenrath, Germany Semiconductor Science and Technology

Vol. 30; 114001

http://dx.doi.org/10.1088/0268-1242/30/11/114001

The full performance of GaN devices for high power applications is not exploited due to their self-heating. Possible solutions are the integration of materials with high heat conductivity i.e., single crystalline diamond and graphene layers. We report the growth of single crystalline (0001)-oriented GaN thin films on (100), (110) and (111) diamond single crystals studied by transmission electron microscopy (TEM) in cross-sections. As for graphene, we show a high quality GaN layer that was deposited on patterned graphene layers and 6H-SiC. The atomic structures of the interfaces in the heterostructure are studied using aberration-corrected scanning TEM combined with energy dispersive x-ray and electron energy-loss spectroscopy.

Properties of sub-band edge states in AlInN studied by time-resolved photoluminescence of a AlInN/GaN heterostructure Saulius Marcinkevičius1, Alexander Sztein2, Shuji Nakamura2 and James S Speck2 1 Department of Materials and Nanophysics, KTH Royal Institute of Technology, Electrum 229, 16440 Kista, Sweden 2 Materials Department, University of California, Santa Barbara, CA 93106, USA Semiconductor Science and Technology

Vol. 30; 114017

http://dx.doi.org/10.1088/0268-1242/30/11/115017

Time-resolved photoluminescence (PL) measurements of Al0.82In0.18N/GaN

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heterostructures revealed a large enhancement of low temperature PL from the GaN layer and a strong temperature dependence of this effect. Analysis of different phenomena that might affect the photoexcited carrier dynamics suggests that the enhanced GaN PL should be attributed to photoexcited hole transfer from the AlInN layer. The hole transport most probably takes place via dense sub-band edge valence band states related to nanoscale In-rich clusters. Scanning near-field optical microscopy data support this assignment.

Zero lattice mismatch and twin-free single crystalline ScN buffer layers for GaN growth on silicon L. Lupina1, M. H. Zoellner1, T. Niermann2, B. Dietrich1, G. Capellini1, S. B. Thapa3, M. Haeberlen3, M. Lehmann2, P. Storck3 and T. Schroeder1,4 1 IHP, Im Technologiepark 25, 15236 Frankfurt, Oder, Germany 2 Technische Universität Berlin, Institut für Optik und Atomare Physik, Straße des 17. Juni 135, 10623 Berlin, Germany 3 SILTRONIC AG, Hanns-Seidel-Platz 4, 81737 München, Germany 4 BTU Cottbus, Konrad-Zuse-Str. 1, 03046 Cottbus, Germany Applied Physics Letters

Vol. 107, 201907 (2015)

http://dx.doi.org/10.1063/1.4935856

We report the growth of thin ScN layers deposited by plasma-assisted molecular beam epitaxy on Sc2O3/Y2O3/Si(111) substrates. Using x-ray diffraction, Raman spectroscopy, and transmission electron microscopy, we find that ScN filmsgrown at 600 °C are single crystalline, twin-free with rock-salt crystal structure, and exhibit a direct optical band gap of 2.2 eV. A high degree of crystalline perfection and a very good lattice matching between ScN and GaN (misfit < 0.1%) makes the ScN/Sc2O3/Y2O3 buffer system a very promising template for the growth of high quality GaN layers on silicon.

Origins of hillock defects on GaN templates grown on Si(111) Y.Han a, D.Zhu a,b, T.Zhu a, C.J.Humphreys a, D.J. Wallis a,b Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK b Plessey Semiconductors, Tamerton Road, Plymouth, Devon PL6 7BQ, UK Journal of Crystal Growth

Volume 434, Pages 123–127

http://dx.doi.org/10.1016/j.jcrysgro.2015.11.005

The origin of surface hillocks (also known as pancake defects) on GaN-on-Si wafers grown by MOVPE has been investigated. FIB/TEM observations confirmed that the appearance of the hillocks is due to the formation of Ga-rich precipitates within the AlGaN buffer layer. XRD (002) FWHM measurements also show that the surface hillocks are associated with a high degree of crystal tilt in the AlN nucleation layer. Two factors are considered to be the cause of such a phase separation: (1) a high density of surface steps associated with the regions of large crystal tilt which act as nucleation centers and (2) a lower mobility of Al adatoms at the growth surface compared with Ga, leading to a preferential incorporation of Ga in the precipitates. The impact of these precipitates on the wafer bow of the structures is considered.

A first-principles study of the mechanical properties of AlN with Raman verification Yiquan Daia, Weihui Wanga, Chengqun Guib, Xiaodong Wenc,d, Qing Pengb,e, Sheng Liub, a Mechanical Sci. & Eng., Huazhong University of Science & Technology, Wuhan 430074, China b Cross-disciplinary Institute of Engineering Sciences, School of Power and Mechanical Engineering, Wuhan University, Wuhan, Hubei 430072, China c State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, China d Synfuels China Co. Ltd Huairou, Beijing 101407, China e Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA

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Computational Materials Science

Volume 112, Part A, Pages 342–346

http://dx.doi.org/10.1016/j.commatsci.2015.09.027

We report calculation to rebuild Raman frequencies detected in Raman scattering of high quality wurtzite-type AlN bulk single crystal. Then, we use this Raman verified mode and parameters to calculate mechanical constants and phonon pressure coefficients, which are all important parameters in Raman based stress detec on. The rela onship between the modes used in Raman rebuilding and constants calcula on are discussed in detail. We have predicted for the rst me View the MathML source2 b under di erent pressures. We have oberserved a new trend that View the MathML source2 b is decreasing slightly according to the pressure, oppose to a constant as assumed. This work is a good foundation for stress/strain analysis used in film and device reliability testing.

Controlling the stress of growing GaN on 150-mm Si (111) in an AlN/GaN strained layer superlattice Po-Jung Lina, d, Shih-Yung Huangb, Wei-Kai Wangc, Che-Lin Chend, Bu-Chin Chungd, Dong-Sing Wuua, c a Department of Materials Science and Engineering, National Chung Hsing University, Taichung 402, Taiwan, R.O.C b Department of Industrial Engineering and Management, Da-Yeh University, Changhua 511 Taiwan, R.O.C c Department of Materials Science and Engineering, Da-Yeh University, Changhua 511 Taiwan, R.O.C d Hermes-Epitek Corporation, Hisinchu 30077, Taiwan, R. O. C Applied Surface Science

http://dx.doi.org/10.1016/j.apsusc.2015.11.226

For growing a thicker GaN epilayer on a Si substrate, generally, a larger wafer bowing with tensile stress caused by the mismatch of thermal expansion coefficients between GaN and Si easily generates a cracked surface during cool down. In this work, wafer bowing was investigated to control stress by changing the thickness of a GaN layer from 18.6 to 27.8 nm in a 80-paired AlN/GaN strained layer superlattice (SLS) grown on a 150-mm Si (111) substrate. The results indicated that wafer bowing was inversely proportional to the

total thickness of epilayer and the thickness of the GaN layer in the AlN/GaN SLS, since higher compressive stress caused by a thicker GaN layer during SLS growth could compensate for the tensile stress generated during cool down. After returning to room temperature, the stress of the AlN/GaN SLS was still compressive and strained in the a-axis. This is due to an unintended AlGaN grading layer was formed in the AlN/GaN SLS. This AlGaN layer reduced the lattice mismatch between AlN and GaN and efficiently accumulated stress without causing relaxation.

Properties of AlN film grown on Si (111)

Yiquan Daia, Shuiming Lia, b, c, Qian Sunb, c, Qing Pengd, e, Chengqun Guid, Yu Zhoub, c, Sheng Liud, a Mechanical Sci. & Eng., Huazhong University of Science & Technology, Wuhan, 430074, China b Key Laboratory of Nanodevices and Applications, Chinese Academy of Sciences (CAS), Suzhou 215123, China c Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences (CAS), Suzhou 215123, China d School of Power and Mechanical Engineering, Wuhan University, Wuhan, Hubei, 430072, China e Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY, 12180, U.S.A. Journal of Crystal Growth

http://dx.doi.org/10.1016/j.jcrysgro.2015.11.016

Stress and strain in an AlN film grown on Si (111) substrate have been evaluated by measuring Raman frequency shifts. Mechanical properties and phonon deformation potentials of AlN are evaluated by first principles calculations. The calculation model is verified by comparing the calculated Raman frequencies and frequencies detected from a bulk single crystal. Results show that the two sets of frequencies agree very well with each other. Thus, with the same verified model and parameters, elastic constants and phonon deformation potentials are calculated. Additionally, we successfully develop a numerical model to verify the calculation above and the model itself is also useful to predict properties of crystal films. Finally, the stress, strain, and piezoelectric properties are analyzed and compared for films on different substrates.

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Optical and structural properties of GaN epitaxial layers on LiAlO2 substrates and their correlation with basal plane stacking faults E.V. Lutsenkoa, M.V. Rzheutskia, V.N. Pavlovskiia, G.P. Yablonskiia, M. Alanzib, A. Hamidalddinb, A. Alyamanib, C. Mauderc, H. Kalischd, B. Reutersd, M. Heukenc, d, A. Vescand, G. Naresh-Kumare, C. Trager-Cowane a B. I. Stepanov Institute of physics of National academy of sciences of Belarus, Nezalezhnasti ave., 68; 220072, Minsk b KACST, National Nanotechnology Center, P.O. BOX 6086 Riyadh – 11442, Saudi Arabia c AIXTRON SE, Dornkaulstr. 2, 52134 Herzogenrath, Germany d GaN Device Technology, RWTH Aachen University, Sommerfeldstr. 24, 52074 Aachen, Germany e Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG, United Kingdom Journal of Crystal Growth

http://dx.doi.org/10.1016/j.jcrysgro.2015.10.036

The optical and structural properties of m-plane GaN layers grown by metal organic vapor phase epitaxy on LiAlO2 (100) substrates were investigated. Temperature-dependent and time-resolved photoluminescence (PL), X-ray diffraction and Raman scattering measurements were performed to analyze the correlation of the sample properties with the density of I1-type basal-plane stacking faults (BSFs). Electron channeling contrast imaging was used to reveal and calculate the density of BSFs reaching the surface of an m-plane GaN/LiAlO2 layer. It was shown that a local increase of BSF density in the investigated samples results in a rise of the total PL efficiency at low temperatures because of the localization of excitons at BSFs and, therefore, a suppression of their diffusion to non-radiative centers. Parameters of time decay and temperature quenching of the BSF-related PL band were determined. A correlation of both εxx and εzz strain components with the BSFs and crystal mosaicity was observed, and possible reasons of this correlation are discussed.

Hybrid density functional study of optically active Er3+ centers in GaN Khang Hoang

Center for Computationally Assisted Science and Technology, North Dakota State University, Fargo,

North Dakota, USA Physica status solidi (RRL) - Rapid Research Letters

http://dx.doi.org/10.1002/pssr.201510269

Understanding the luminescence of GaN doped with erbium (Er) requires a detailed knowledge of the interaction between the rare-earth dopant and the nitride host, including intrinsic defects and other impurities that may be present in the host material. We address this problem through a first-principles hybrid density functional study of the structure, energetics, and transition levels of the Er impurity and its complexes with N and Ga vacancies, substitutional C and O impurities, and H interstitials in wurtzite GaN. We find that, in the interior of the material, ErGa is the dominant Er3+ center with a formation energy of 1.55 eV, ErGa–VN possesses a deep donor level at 0.61 eV which can assist in the transfer of energy to the 4f -electron core. Multiple optically active Er3+ centers are possible in Er-doped GaN.

Temperature-dependent cathodoluminescence investigation of Er-implanted GaN thin films Yajuan Mo1, Xiaodan Wang1,*, Mingming Yang2, Xionghui Zeng2,*, Jianfeng Wang2 and Ke Xu2 1Department of Physics, Suzhou University of Science and Technology, Suzhou, P.R. China 2Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou, P.R. China Physica status solidi (b)

http://dx.doi.org/10.1002/pssb.201552470

In this paper, temperature-dependent cathodoluminescence (CL) spectra of Er-implanted GaN thin films were measured. The effects of accelerating voltage and temperature on the CL spectra of Er-implanted GaN were investigated. In the near band-edge emission region, the competition mechanism between DAP and D0X was disclosed. A slight blue shift of the DAP emission peak with the increase of accelerating voltage was observed. The temperature dependence of the CL intensity of FX emission reveals a binding energy of ∼32 meV in Er-implanted GaN. Below 182 K, the 2H11/2 state of Er3+ is not thermally populated and the yellow band luminescence (YL) related to the defects was observed. At higher temperature, the thermal

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coupling between the two excited state levels of 2H11/2 and 4S3/2 of Er3+ is obvious and the YL is nearly invisible. Even at 373 K, a strong green emission at 537 nm can be observed, which indicates the Er-doped GaN is promising to be applied in high-temperature environments.

Effect of nitridation surface treatment on silicon (111) substrate for the growth of high quality single-crystalline GaN hetero-epitaxy layer by MOCVD R. Nazri, Y. Yusnizam, M. Mazwan, A. Shuhaimi

Department of Physics, Low Dimensional Materials Research Centre (LDMRC), University of Malaya, 50603, Kuala Lumpur, Malaysia Applied Surface Science

http://dx.doi.org/10.1016/j.apsusc.2015.10.226

A single-crystalline with high quality of gallium nitride epilayers was grown on silicon (111) substrate by metal organic chemical vapor deposition. The process of nitridation surface treatment was accomplished on silicon(111) substrate by flowing the ammonia gaseous. Then, it was followed by a thin aluminum nitride nucleation layer, aluminum nitride/gallium nitridemulti-layer and a thick gallium nitride epilayer. The influence of in situ nitridation surface treatmenton the crystallinity quality of gallium nitride epilayers was studied by varying the nitridation times at 40, 220 and 400 seconds, respectively. It was shown that the nitridation times greatly affect the structural properties of the grown top gallium nitride epilayer on silicon (111) substrate. In the (0002) and (View the MathML source101¯2) x-ray rocking curve analysis, a narrower value of full width at half-maximum has been obtained as the nitridation time increased. This is signifying the reduction of dislocation density in the gallium nitride epilayer. This result was supported by the value of bowing and root mean square roughness measured by surface profilometer and atomic force microscopy. Furthermore, a crack-free gallium nitride surface with an abrupt cross-sectional structure that observed using field effect scanning electron microscopy was also been obtained. The phi-scan

curve of asymmetric gallium nitride proved the top gallium nitride epilayer exhibited a single-crystalline structure.

Study of Al diffusion in GaN during metal organic vapor phase epitaxy of AlGaN/GaN and AlN/GaN structures N. Chaaben, J. Laifi, H. Bouazizi, C. Saidi, A. Bchetnia, B. El Jani Unité de Recherche sur les Hétéro-Epitaxies et Applications Faculté des Sciences de Monastir 5019, Université de Monastir, Tunisia Materials Science in Semiconductor Processing

http://dx.doi.org/10.1016/j.mssp.2015.11.008

AlxGa1−xN/GaN hetero-structures were grown on SiN-treated (00.1) sapphire substrate by atmospheric pressure metalorganic vapor phase epitaxy (AP-MOVPE). Characterization of the grown structures was performed in-situ by laser reflectometry and ex-situ by secondary ion mass spectrometry (SIMS) measurements. Al SIMS profile showed some tailing to GaN layers which is associated to Al diffusion. The trimethylaluminium (TMA) effects on the growth rate, Al composition and Al diffusion coefficient were discussed. Al diffusion coefficients (DAl) into GaN were calculated. The results suggest that Al diffuses faster near the AlN/GaN interface.

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PRESS RELEASE Technical and economic information selected by Knowmade

OPTOELECTRONICS

Osram investing €3bn in lighting by 2020 Semiconductor Today

In response to the shift in the lighting market toward semiconductor-based technologies creating new growth opportunities, lighting company Osram GmbH of Munich, Germany says that it is to invest about €3bn in new technologies and applications by 2020. Of this amount, about €2bn will be spent on research and development in order to further strengthen Osram's technology and to expand into new markets. Additionally, Osram plans to spend a further €1bn in constructing a new LED chip plant in Malaysia, in order to unlock additional growth potential in both dynamic, technology-driven general lighting markets and niche markets, where Osram is already present. "With a focus on profitability, flexibility and entrepreneurship, following a phase of strategic realignment, we are now launching the 'Diamond' innovation and growth initiative," says Osram Licht AG's CEO Olaf Berlien. "This means we are switching the focus to sustainable growth, benefitting even stronger from the potential offered by semiconductor-based technologies," he adds. 'Diamond' comprises several strategic measures. In a first step, Osram will invest about €370m in its Opto Semiconductors (OS) segment for a new LED chip plant in Kulim, Malaysia. Since further expansion measures are already being planned, the firm expects to invest a total of about €1bn there by 2020. The new plant is expected to represent the largest 6-inch LED chip production site worldwide. Osram expects that the additional production capacity and its technology should enable it to significantly increase its market share in the fast-growing general lighting market (which is currently about €5.7bn). Given average annual growth rates of 7.5%, the firm reckons that this

offers the greatest potential up to 2020. It also reckons that, through economies of scale and synergies, it can also reduce its costs in other market activities such as automotive lighting as well as applications for mobile devices, in which Osram already has a strong presence. Osram is also planning additional investments in the Specialty Lighting (SP) segment to facilitate the broad-based rollout of new technologies in the market and to realize further growth potential. The firm has been the global leader in automotive lighting for many years, and intends to strengthen activities with innovative lighting modules. For example, Osram is claimed to be the only company in the world currently offering laser modules for headlamps ready for series production. Also for automotive lighting, organic light-emitting diode (OLED) technology is about to be rolled out for broad-based use in the rear lights of vehicles. Osram expects the market for laser and OLED applications in the automotive sector to amount to about €1.1bn in 2025. In the recently created Lighting Solutions & Systems (LSS) segment, Osram says it will roll out many different measures in the coming years to realize ‘‘intelligent, technologically demanding lighting solutions’‘. Following the review of the luminaires and solutions business (LS) announced recently, Osram says it is aligning this segment towards profitable growth. In particular, the market entry and range of integrated solutions offered are to be improved, adds the firm. Given the increasing importance of complex lighting solutions, Osram is also shifting the focus to expanding its electronics and software expertise. Over the next two years, new capacities for electronic ballasts and light management systems will be created for this purpose. Boost to research In line with the initiatives announced, Osram aims to increase its R&D budget significantly, aiming in particular to promote development of smart-city

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applications, wireless lighting control, and laser and OLED technology. Osram says that, despite consolidation and focusing measures, it has kept its research at a high level of just over 6% of revenue in recent years. After the sell-off of its general lighting lamps business that was initiated recently, the increased research expenditure will account for about 9% of revenue by fiscal-year 2016. "Investments in research and development have paid off for the company in the past by taking it to a clear number-one position in the automotive sector and leading to groundbreaking applications with opto semiconductors," says Berlien. "Through the intended increase in research intensity, Osram wants to further strengthen its technical expertise for semiconductor-based technology and extend its market position." 'Diamond' targets growth The 'Diamond' innovation and growth initiative aims to increasingly focus the company on balanced growth. In addition to high-revenue areas that hold large growth potential, lucrative niche areas - where Osram is already in a good position - will continue to make a valuable contribution to overall returns, the firm reckons. Osram has hence set the following targets, to be achieved in fiscal 2020: •revenue of €5-5.5bn (corresponding to an average annual growth rate of 8%, after the sell-off of the lamps business); •earnings before interest, tax, depreciation, and amortization (EBITDA) of €0.9-1bn (correspond to an average annual growth rate of about 9%); and •earnings per share of about €5 (equivalent to an average annual increase rate of around 25% compared with fiscal 2015) - the announced share buyback program is included in this target.

Read more DOE announces 2016 funding opportunity for solid-state lighting R&D Semiconductor Today

The US Department of Energy (DOE) has announced the 'Solid-State Lighting Advanced Technology R&D—2016' funding opportunity (DE-FOA-0001364)), under which a total of up to

$10.5m in funding is directed toward all three existing DOE solid-state lighting (SSL) R&D program areas for both light-emitting diode (LED) and organic light-emitting diode (OLED) technologies: •Core Technology Research — the application of fundamental scientific concepts to SSL technology; •Product Development — using the knowledge gained from basic or applied research to develop or improve commercially viable SSL materials, devices, or systems; •US Manufacturing — accelerating SSL technology adoption through manufacturing innovations and improvements that reduce costs and enhance quality and consistency.

The objectives of this latest funding opportunity are to: maximize the energy efficiency of SSL products in the marketplace; remove market barriers through improvements to lifetime, color quality, and lighting system performance; reduce costs of SSL sources and luminaires; improve product consistency while maintaining high-quality products; and encourage the growth, leadership and sustainability of domestic US manufacturing within SSL industry The DOE will select up to 10 projects. Concept papers are due by 20 November and full applications are due by 20 January 2016. Read more Plessey demonstrating modular smart lighting system at LuxLive Semiconductor Today

In stand E26 at the LuxLive lighting trade show in London, UK (18-19 November), UK-based Plessey is demonstrating the potential uses of its gallium nitride on silicon MAGIC (Manufactured on GaN-on-Si I/C) LED technology with a new smart lighting product called Totem, developed in collaboration with Manchester-based product design consultancy inventid. Totem is said to be an original concept based on the use of LED lighting solutions in the Internet of Things (IoT) - an increasingly favoured solution for the development of smart homes and cities. "Our LED technology permits a far more integrated solution compared to traditional white LED components," claims Plessey's product line

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director Neil Harper. "Our integrated intelligent LEDs provide the design freedom to ensure end applications have greater functionality. Such things as dimming functions, light colour adjustment, automatic switch controls and remote operation can all be integrated into the silicon-based MAGIC LED," he adds. "The team at inventid came up with a huge number of ideas and the first application we thought would resonate at the LuxLive event was the concept of the hands-free home," Harper continues. ‘‘The Totem could also include other modules like ambient light sensor, sound and real-time clock whilst also fully controllable by consumers, providing dual functionality both as an addressable and reactive smart-lighting product. Together, we have designed Totem to deal with genuine human needs in the areas of safety and security, wellness, energy management and entertainment," he adds. "The Totem is designed to be discreet and simple yet maintain strong ties with its heritage; the traditional light bulb," says inventid's co-founder Henry James. "Lights help change the use of a room and, because there are lights in every room in every home, they have the potential to reach people in a way that no other product can. In the same way that you can drive your car and speak on your mobile hands-free, you should be free to move about your house and talk hands free - the use of the light bulb to perform this function is a bit of genius." Read more Plessey and 8Point3 to produce high-efficiency LED architectural lighting Semiconductor Today

Plessey has collaborated with fellow UK-based firm 8Point3 Ltd (a provider of energy-saving, solid-state lighting solutions for both the private and public sectors, and a Value Add Partner of Philips Lighting) to develop and produce a high-efficiency architectural lighting product range. Plessey has signed a long-term commercial agreement with 8point3 to supply the lighting modules, including its gallium nitride on silicon MaGIC (Manufactured on GaN-on-Si I/C) LEDs. "The improvements we have made on efficiency by using Plessey LEDs shows our continued

commitment to developing and refining our products," says 8point3's managing director Ashley Bateup. The Sabre linear lighting products combine the benefits of remote phosphor with a unique LED light engine, offering what are claimed to be unprecedented system efficiencies and an economic life-cycle. With a wide range of colour temperatures, Sabre provides a uniform and diffuse luminance and appearance, ensuring no reflections or pixilation, even when dimming the light, it is claimed. It offers designers a flexible solution for high-lumen areas and decorative lighting systems and is being widely used in the hospitality and retail sectors. "Increased efficiencies have been achieved thanks to the close working partnership between our team of engineers and 8point3," comments Plessey's regional sales manager Mark Pinnock. "The Sabre architectural range shows what is possible when UK innovators join forces." Plessey is holding product demonstrations presented by technical and design experts at stand E26 at LuxLive (the UK largest lighting show) at London's ExCeL arena (18-19 November), where the firm is demonstrating its latest products and solutions for the commercial, industrial, consumer and wearable lighting segments. Read more Plessey named 2015 Company of the Year by the NMI Semiconductor Today

At an annual awards ceremony in London attended by more than 350 guests from the UK electronic systems industry, UK-based Plessey has been named Company of the Year by the NMI (National Microelectronics Institute), the industry trade body for electronic systems in the UK & Ireland. "We present awards to recognize the achievements and behaviours that are conducive to a healthy and vibrant electronics industry in the UK and Ireland," says NMI's chief executive Dr Derek Boyd. "Our awards showcase excellence within the industry rewarding the innovation, expertise and ambition of businesses," he adds.

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Picture: Receiving the award for Plessey: IC design manager George Ostaszewski, QA manager Robin Steele, product design director Neil Harper, financial director Chris Bailey, chief technology officer Dr Keith Strickland and commercial operations director Alan Colman.

"We are entering a very exciting period with our new LED technology," said Plessey's chief technology officer Dr Keith Strickland at the event. "Our products are now gaining market traction in one of the fastest-growing technology markets, solid-state lighting. The expansion is highly significant not only for Plessey, but also for British high-tech manufacturing," he adds. "We expect that our award-winning MaGIC [Manufactured on GaN-on-Si I/C] GaN-on-silicon technology with integrated electronics and optics will be soon be used around the world in a variety of lighting applications." In September, Plessey announced a major expansion of its LED manufacturing facility in Plymouth, UK, after securing a £30m loan from Deutsche Bank AG to finance the expansion. Read more Rensselaer's Michael Shur wins IET Achievement award for DUV LED research Semiconductor Today

Rensselaer Polytechnic Institute (RPI) in Troy, NY, USA says that Michael Shur (its Patricia W. and C. Sheldon Roberts Professor of Solid State Electronics) is to receive an Achievement award from the UK's Institution of Engineering and Technology (IET) for pioneering contributions to deep-ultraviolet light-emitting diode (DUV LED) technology.

The IET Achievement Awards recognize individuals from around the world who have made exceptional contributions to the advancement of engineering, technology and science in any sector, either through research and development in their respective technical field or through their leadership of an enterprise. "It is a fitting recognition of his outstanding work at the intersection of advanced materials, devices and integrated systems," comments Rensselaer's dean of engineering Shekhar Garde. "The tremendous productivity and impact of his research group is a great example of the vibrancy of our Electrical and Computer Systems Engineering Department, which is home to several prominent research centers." Shur's research in solid-state devices focuses on plasma wave excitation in submicron field-effect transistor (FET) and related device structures. His research has shown that a short-channel FET has a resonance response to electromagnetic radiation at the plasma oscillation frequencies of the two-dimensional electrons in the device. The device that uses this resonance response should operate at much higher frequencies than conventional transit-time-limited devices – in the terahertz range – since the plasma waves propagate much faster than electrons. Shur joined the Rensselaer faculty in 1996 and was named the Patricia W. and C. Sheldon Roberts Professor of Solid State Electronics. He has also held faculty positions at Wayne State University, Oakland University, and the University of Minnesota. Recipients will be honored at the IET's awards ceremony on 18 November, in conjunction with the announcement and presentation of the IET Volunteer Medal in London, UK. Read more Chinese market for packaged LEDs to grow at single-digit annual rate Semiconductor Today

Due to oversupply and price competition between the suppliers of lighting LEDs, the total Chinese market for packaged LEDs will grow at a single-digit annual rate, forecasts market research firm IHS. The total Chinese market for packaged LEDs was $6.7bn in 2014, including $3.8bn for lighting

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applications, according to the latest data in the 'Packaged LEDs Report – China – 2015' (part of the IHS LED Intelligence Service).

Since too many suppliers produce almost the same LEDs for lighting (e.g. using the 2.8mm x 3.5mm 2835-type LED chip size), the average selling price (ASP) declined significantly in 2015. To ensure revenue growth, different companies therefore use different strategies. Larger companies tend to grow through capacity expansion and acquisition (for example, Hongli acquired Smalite, and Refond acquired Lingtao). Meanwhile, smaller companies are finding it difficult to survive without further investment or a unique technical advantage. In China in 2014, Nichia had the highest revenue, followed by MLS and Everlight. In addition to MLS, other local suppliers (such as Nationstar) have started to play an important role and are growing quickly, notes the report. Look just at the revenue of China-based companies, MLS was number one in 2014, followed by Nationstar and Jufei. MLS also had the highest revenue in lighting, signage and 'other' sectors, whereas Jufei led in the backlighting and mobile sectors. Eight Chinese companies had packaged LED revenue of more than $100m in 2014, concludes IHS. Read more

ELECTRONICS

GaN Systems' launches half-bridge evaluation board for GaN transistor circuit design Semiconductor Today

GaN Systems Inc of Ottawa, Ontario, Canada, a fabless developer of gallium nitride (GaN)-based power switching semiconductors for power conversion and control applications, has launched its Half-Bridge Evaluation Board, which demonstrates the performance of its GaN enhancement-mode power semiconductors in real power circuits. The fully functional GS66508T-EVBHB Eval Board can be configured into any half-bridge-based topology, including boost and buck modes. It comes with a Quick Start instruction guide and YouTube video links (www.youtube.com/user/GaNSystems) in order to have the installation up and running in minutes. The Eval Board can be used in synchronous boost or buck conversion, as well as pulsed switching to evaluate transistor waveforms. The kit has full documentation, including bill-of-materials component part numbers, PCB layout and thermal management, and gate drive circuit reference design, which is also useful for system engineers to use in their products. Designed to provide electrical engineers with a complete working power stage, the evaluation board consists of two 650V, 30A GS66508T GaN FETs, half-bridge gate drivers, a gate drive power supply, and heat-sink. The GS66508T high-power transistors are based on GaN Systems' proprietary Island Technology and belong to its 650V family of high-density devices, which achieve efficient power conversion with fast switching speeds of >100V/nS and ultra-low thermal losses, the firm says. GaN Systems claims to be the only company to have developed and productized a comprehensive portfolio of GaN power transistors with voltage ratings of 100V and 650V and current ratings from 7A to 250A. Its Island Technology die design, combined with the very low inductance and thermal efficiency of GaNPX packaging, provides the GaN FETs with a 45x improvement in switching and conduction performance over traditional silicon MOSFETs and IGBTs, the firm adds. The 30A/55mΩ GS66508T GaN power transistors are top-side cooled and feature near-chip-scale thermally efficient GaNPX packaging. Power conversion efficiency of 98.7% at 1.5kW is shown in the product documentation and can be reproduced in the owner's lab.

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The Eval Board provides footprints for output power inductors and capacitors to allow users to configure the board into desired boost or buck operational modes. Access to the transistor junction temperature is provided by both thermocouple pads and thermal camera imaging ports. Power input should be 9-12VDC, with an absolute maximum of 15V. On-board voltage regulators create +5V for the logic circuit and +6.5V for the gate driver. There are three operational modes: pulse test mode; buck/standard half-bridge mode and boost mode. The GS66508T high-current half-bridge Evaluation Board is available now worldwide and can be sourced by searching the GS66508T-EVBHB part number to find a local authorised distributor. Read more WIN expands GaN portfolio by adding 0.45μm-gate GaN-on-SiC power process for 4G/5G macro-cell base-station power amplifiers Semiconductor Today

WIN Semiconductors Corp of Tao Yuan City, Taiwan - a pure-play provider of gallium arsenide (GaAs) and gallium nitide (GaN) wafer foundry services for the wireless, infrastructure and networking markets – has expanded its GaN technology portfolio by adding the NP45 gallium nitride on silicon carbide (GaN-on-SiC) process. NP45 is a 0.45μm-gate MMIC technology enabling users to design fully integrated amplifier products as well as custom discrete transistors, and has been optimized for use in 4G macro-cell base-station power amplifiers operating at 2.7GHz and above, where bandwidth and linearity performance are key differentiators. The macro-cell base-station power amplifier market is projected to grow to more than $1bn annually by 2020, and GaN technology is expected to become the technology of choice for this application, says WIN. Due to its efficiency, bandwidth and linearity, GaN devices outperform the incumbent LDMOS silicon technology, particularly in the higher-frequency bands utilized in 4G/4.5G networks, claims WIN. The WIN NP45 process technology is fabricated on 100mm silicon carbide substrates and operates at a drain bias of 50V. In the 2.7GHz band this technology provides saturated output power of

7W/mm with 17dB linear gain and more than 75% power-added efficiency. These performance metrics make NP45 suitable for use in high-bandwidth 4G-5G high-power macro-cell transmitters and small cells, says WIN. NP45 sample kits are available and can be obtained by contacting the firm's regional sales managers. Read more Qorvo's quarterly revenue rises 5.2%, led by Mobile Products Semiconductor Today

For its fiscal second-quarter 2016 (ended 3 October 2015), Qorvo Inc, which provides core technologies and RF solutions for mobile, infrastructure and aerospace/defense applications, has reported revenue of $708.3m, up 5.2% on $673.6m last quarter and up 12% on $634.8m a year ago for the combined September 2014 quarter revenues of RF Micro Devices Inc of Greensboro, NC and TriQuint Semiconductor Inc of Hillsboro, OR, USA (following the merger of the two firms on 1 January). The top three customers comprised about 60% of revenue, including two 10%-or-more customers. The largest, at 41%, represents the aggregate of multiple subcontractors for this end customer. The second is China-based telecoms equipment maker Huawei Technologies Co Ltd (a customer for both Mobile Products and Infrastructure & Defense Products). Both the Mobile Products and Infrastructure & Defense Products (IDP) businesses did better than expected. Despite rising 6% from $122m last quarter, Infrastructure & Defense Products revenue of $129m was down 13% year-on-year, due to wireless infrastructure falling about $24m on a year ago. However, outside of wireless infrastructure, IDP revenue grew about 6% year-on-year. Growth was led by Mobile Products, for which revenue grew 19% year-on-year and 5% sequentially (from $551m last quarter) to $578m, driven by large customer product ramps. However, following strong growth in China in the first two quarters of calendar 2015 (including a $100m rise in the June quarter), despite continued strength from Qorvo's largest customer in the

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country, other Chinese customers have since slowed (not achieving their goals set at the beginning of the year), according to Mobile Products president Eric Creviston. On a non-GAAP basis, gross margin was 49.7%, up from 47.4% a year ago but down from 51.5% last quarter (and slightly below the guidance of 50-51%) due to product mix. Operating expenses (OpEx) were cut by nearly $2m from $158.7m last quarter to $156.8m, reflecting synergies that have been realized. Year-on-year, operating expenses grew at half the rate of revenue growth. In particular, R&D expenses rose 14% sequentially as Qorvo pursued major growth opportunities, while sales & marketing and general administrative expenses rose 14% year-on-year. ‘‘The realization of synergies is allowing Qorvo to appropriately invest in product and process development, while driving towards our operating expense model,’‘ says Creviston. Operating income was $194.8m (an operating margin of 27.5% of revenue), up on $187.8m last quarter and up 28% on a year ago. This was led by the Mobile Products business unit, which achieved operating income of about 30% on its 19% revenue growth. ‘‘In the nine months since Qorvo's formation, revenue has grown 25% from the same period in the prior year while non-GAAP operating income has nearly doubled,’‘ notes chief financial officer Steve Buhaly. Net income rose from $168.5m ($1.09 per diluted share) last quarter to $183.3m ($1.22 per diluted share, exceeding the original guidance of $1.10). Cash flow from operations was $168.8m (up from $141.4m last quarter). Capital expenditure (CapEx) was $80.3m, primarily to address growth and demand for premium filters. During the quarter, Qorvo repurchased about 9.1 million shares of its common stock at a total cost of $500m. Overall, cash and investments have fallen hence from $558m to $195.6m. Since the end of the quarter, Qorvo's board of directors has just authorized a new one-year $1bn share repurchase program (expiring on 4 November 2016). ‘‘Design activity during the quarter was particularly robust, as we secured multiple opportunities to expand content in the marquee smartphones launching in calendar 2016 and 2017 and positioned IDP to accelerate growth across its

target markets,’‘ notes president & CEO Bob Bruggeworth. In mobile, Qorvo entered the BAW-based multiplexer market with a family of quadplexers for smartphones supporting carrier aggregation in China and Europe. Those parts are sampling at leading customers, with volume production expected in the spring. Collaborating with leading channel partners in China, Qorvo also captured multiple next-generation LTE reference design wins for multimode power amplifiers (PAs), multimode transmit modules, switches, duplexers and multiplexers. ‘‘Qorvo has excellent long-term opportunities in China as smartphones continue to proliferate, as customers in China increase the number of phones they export, and as the RF content in China-based smartphones continues to expand,’‘ says Bruggeworth. In IDP, Qorvo enjoyed strong design-win activity and signed multiple long-term supply agreements in defense & aerospace. In connectivity, the firm secured multiple high-value 5GHz PA and BAW filter slots in high-performance Wi-Fi enterprise applications and expanded mobile Wi-Fi content with a leading LTE reference design provider. In transport, Qorvo captured an increasing percentage of DOCSIS 3.1 sockets with highly differentiated hybrid GaAs and GaN products delivering what is claimed to be best-in-class efficiency, bandwidth and power. ‘‘In cable TV, Qorvo was especially strong with hybrid GaAs and GaN power doublers, saving operators 15-20W,’‘ says Bruggeworth. ‘‘These solutions mix and match our legacy technologies and capability, and they are especially strong in power efficiency and needed in applications where power consumption is everything,’‘ he adds. In wireless infrastructure, Qorvo was an active participant in pre-5G and 5G demos at major base-station OEMs, and it sampled GaN-based macro-cell high-power amplifier (HPAs) to the five leading base-station OEMs. ‘‘We are introducing an expanded set of new products combining switches and filters and leveraging our broad set of competencies, including BAW filter and GaN process technologies, and all of this is creating exciting new growth opportunities for Qorvo,’‘ says chief financial officer Steven J. Buhaly.

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‘‘Our IDP organization has essentially repositioned itself to accelerate growth above what our legacy IDP businesses had achieved historically,’‘ notes Bruggeworth. ‘‘IDP is structured around a diverse portfolio of businesses, all leveraging Qorvo's shared core competencies and focused on winning with premium products using highly differentiated internally developed technologies. We're increasing our focus on automotive, Internet of Things, data centers and Wi-Fi, and we're increasing our resources in those value streams. We're also targeting segments that don't appear to enjoy the same dynamic growth but have large niches that can be exploited with differentiated products based on Qorvo's technology,’‘ he adds. Examples include Qorvo's GaN-based products in the base-station market, and in the traveling-wave tube (TWT) replacement to defense and commercial markets using the firm's patent-protected Spatium solid-state products. ‘‘We're continuing to penetrate the defense market with our expanding family of GaN-based products and we're increasing our leading market share, as measured by Strategy Analytics,’‘ Bruggeworth says. ‘‘IDP is targeting the highest-growth segments within their diversified businesses with compelling premium solutions using highly differentiated internally developed technologies,’‘ continues Bruggeworth. ‘‘They're moving the organization forward from pre-merger levels, where both companies saw low growth trajectories [of 5-7 percentage points], to today where we see IDP on a path to grow their business two times to three times those legacy growth rates,’‘ he adds. ‘‘You'll start to see our growth rates pick up as we go into next year and certainly as we move into 2017 and 2018,’‘ adds IDP president James L Klein. ‘‘In China, we saw industry fundamentals begin to improve and believe base-station customer activity bottomed in the September quarter,’‘ says Bruggeworth. ‘‘We remain cautious and believe we've embedded conservative expectations in our forward guidance related to China-based handset demand.’‘ For its fiscal third-quarter 2016 (ending 2 January 2016), Qorvo expects revenue of $720-730m. Gross margin should return to about 50%, aided by benefits from the consolidation of assembly & test in China accruing in the second half of

calendar 2015. OpEx should again be in the mid-$150m. Diluted EPS should be $1.25-1.30. ‘‘Synergy achievement is on track [expected to beat the $75m annual target for both year one and year two post-merger], led by the consolidation of test & assembly into our China operations,’‘ notes Buhaly. ‘‘We're also uniquely positioned to reduce cost and enhance our operating model,’‘ reckons Bruggeworth. ‘‘Our two largest synergy opportunities remains the in-sourcing of packaging, assembly & test, and the in-sourcing of SAW filters. We estimate these represent greater than $60m in annualized savings,’‘ he adds. ‘‘They're progressing on schedule and the benefit is expected to favorably impact results beginning early next year.’‘ ‘‘We think calendar 2016 will be a strong year for Qorvo and believe we will fully achieve our target operating model of 30% operating margin over the full year,’‘ concludes Buhaly. Read more MACOM receives first production order for SPAR tiles in Multifunction Phased Array Radar Semiconductor Today

M/A-COM Technology Solutions Inc of Lowell, MA, USA (which makes semiconductors, components and subassemblies for analog RF, microwave, millimeter-wave and photonic applications) says that, following the field trial of the Multifunction Phased Array Radar (MPAR) prototype system, the Massachusetts Institute of Technology (MIT) Lincoln Laboratory has placed an order for Scalable Planar ARray (SPAR) Tiles for use in the first full-scale MPAR system. SPAR Tiles are RF assemblies containing antenna elements, gallium arsenide (GaAs) and gallium nitrride (GaN) semiconductors, transmit and receive modules, and RF and power distribution networks. When combined with additional signal generation and receive and control electronics, the composite assembly forms the building block for the MPAR planar active electronically scanned antenna (AESA) for the radar system. SPAR Tiles enable the transition from cumbersome traditional brick architectures to a more efficient planar approach. MACOM says that, by leveraging its commercial manufacturing expertise, SPAR Tiles will help to drive cost

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efficiencies that are required to propel MPAR to mainstream adoption and deployment in the latter part of this decade. The MPAR radar system enables enhanced temporal and spatial precision for weather surveillance and air-traffic control applications. It is anticipated that the government proof-of-concept system will demonstrate a unique radar capability that simultaneously improves both aircraft and weather surveillance. The data gathered by the MPAR radar can be used by the National Oceanic and Atmospheric Administration (NOAA) to more accurately forecast severe storm activity, providing the early warning needed to save lives. The Federal Aviation Administration's (FAA) current air-traffic control network, built more than three decades ago, is approaching obsolescence. It is believed that replacing these systems with MPAR would provide improved awareness of air-traffic patterns, bringing dramatic efficiency improvements to FAA air traffic operations. ‘‘The implementation of MACOM's SPAR Tiles as a critical element of a full-scale demonstration of MPAR represents a major milestone in the validation of this new approach for manufacturing AESAs,’‘ says Dr Doug Carlson, vice president, Strategy, at MACOM. ‘‘SPAR Tiles enable new levels of affordability and flexibility across a broad range of civil and defense applications,’‘ he adds. ‘‘Our ability to fulfill large orders of SPAR Tiles demonstrates the scalability of our manufacturing approach to achieve volume production of this highly integrated and complex RF product.’‘ Read more VisIC makes available evaluation board and samples for 650V GaN power switch Semiconductor Today

After in June launching what it claimed was the lowest-resistance 650V-blocking-voltage transistor (specifying an Rdson as low as 15mOhm), VisIC Technologies Ltd of Rehovot, Israel, a fabless developer of devices based on gallium nitride (GaN) metail-insulator-semiconductor high-electron-mobility transistors (MISHEMTs) founded in 2010, has now delivered evaluation boards (EB) and samples of its ALL-Switch (Advanced Low-Loss Switch) to leading customers, allowing users to

perform extensive testing confirming the switching parameters.

Picture: ALL-Switch evaluation board.

The evaluation board includes gate driver and switching control logic based on commercially available components. ALL-Switch is configured for hard switching on the evaluation board and can switch a 400V load with greater than 30A currents at over 500kHz. VisIC says that its technology solves problems that have limited devices from simultaneously achieving step-function reductions in conduction and switching losses for power conversion systems that can benefit from high switching speeds. VisIC will soon also announce details of a half-bridge reference design. Read more Lockheed Martin introduces GaN-based Digital Array Row Transceiver radar technology Semiconductor Today

At its regular radar users' conference in Orlando, FL (attended by representatives from more than 25 countries), security and aerospace company Lockheed Martin of Bethesda, MD, USA has unveiled its Digital Array Row Transceiver (DART) next-generation radar technology. Based on the use of gallium nitride (GaN) technology, DART results in greater performance within existing Lockheed Martin radar products and lowers life-cycle costs due to an increase in energy efficiency. The firm says that GaN is a low-

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risk solution, whether part of a systems upgrade or in a newly built system. DART improves on Lockheed Martin's ground-based radar products. The new technology is available in the recently launched TPS-77 Multi Role Radar system and is fully compatible with legacy products (TPS-77, TPS-59, FPS-117) and can help to extend a radar's useful life. ‘‘This technology is based in part on feedback we have received from customers with whom we've developed strong partnerships over decades,’‘ says Mark Mekker, Lockheed Martin's director, surveillance radar. Lockheed Martin has produced and maintains more than 175 surveillance-range radars, which are operational around the world detecting targets at ranges up to 250 miles, 24 hours a day. These radars are capable of operating completely unmanned and many have performed for decades in remote, inhospitable areas and in a wide range of operational environments, says the firm. Lockheed Martin notes that no FPS-117, TPS-77 or TPS-59 radar has ever been taken out of service, and the systems continue to operate well beyond their original 20-year service lives (many are planned to operate for more than 40 years). Read more TMS launches modular line of non-ITAR 0.1-6.0GHz GaN amplifiers with small form factor for harsh airborne requirements Semiconductor Today

Teledyne Microwave Solutions Inc of Mountain View, CA, USA (TMS, a business unit of Teledyne Technologies Inc) has launched a line of gallium nitride (GaN)-based wideband amplifiers that is claimed to further lower the form factor threshold for the 0.1-6.0GHz frequency range. The new line consists of five GaN wideband amplifier models (TSA-213241, TSA-213242, TSA-213243, TSA-213244 and TSA-213245) that are claimed to raise the bar for SWaP (size, weight and power) in this category of GaN amplifiers while meeting the stringent airborne requirements of the most demanding commercial and military applications. The dimensions (excluding connectors) are 2.5’‘ long by 2’‘ wide by 0.42’‘ high (just 2.1 cubic inches).

TMS says that it has created a modular, non-ITAR line of amplifiers that it can quickly tailor to the specific needs of customers. With wider bandwidths that enable more design flexibility, the new GaN amplifier line targest the most demanding SWaP needs of airborne markets. ‘‘This GaN line is the latest addition to the portfolio we have developed over decades, including our AVP catalog series,’‘ says Dan Cheadle, chief technology officer of Cougar Products for Teledyne Microwave Solutions. ‘‘Leveraging the high power output and high efficiency of GaN, these amps offer a durable GaN solution that delivers the highest output power over wide bandwidths in the smallest footprint possible today.’‘ This family of amplifiers was designed and manufactured with attention to thermal requirements to ensure the high reliability required in the most demanding applications. With a calculated mean time between failures (MTBF) of over 40,000 hours @ +85°C, the amplifiers are suitable for airborne applications as well as challenging land-based environments. Depending on frequency band, the output power ranges between 15W and 40W. Each amplifier includes pre-amp and driver stages to produce a minimum overall gain of 50dB. Internal control circuitry ensures safe startup so supply voltages can be applied in any order. In addition to normal DC connections via a 15-pin Micro D connector, other control/interface features available via the connector include a TX enable/disable TTL command (100ns typical, 200ns maximum); over-temperature automatic shutdown and associated alarm (TTL); and the ability to monitor unit temperature via an analog voltage that is proportional to case temperature. Read more

OTHER

Rubicon's Q3 revenue hit by LCD TV backlighting slowdown and customers' excess inventory Semiconductor Today

For third-quarter 2015, Rubicon Technology Inc of Bensenville, IL, USA (which makes monocrystalline sapphire substrates and products for the LED,

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semiconductor and optical industries) has reported revenue of $5.3m, down on $7.1m last quarter and $8m a year ago due to weaker sapphire demand. Fiscal Revenue Q3/2014 : $8m Q4/2014 : $8.9m Q1/2015 : $8.9m Q2/2015 : $7.1m Q3/2015 : $5.3m Total revenue for sapphire cores is down from $4.2m a year ago and $4m last quarter to $1.8m. This is due to revenue for 2-inch cores sold into the mobile device market plummeting from $2.6m last quarter to just $0.55m (below the $0.86m a year ago) as a result of higher inventory levels of finished 2-inch double-side-polished wafers (for the mobile device market) at customers. Revenue from 6-inch cores has fallen back from $0.17m last quarter to just $0.04m. Revenue from 4-inch cores for the LED market was flat on last quarter's $1.2m and down on $3.3m a year ago, as pricing declined further. ‘‘This is also likely to be related to excess inventory in the LED supply chain due to reduced demand from the backlighting market,’‘ says president & CEO Bill Weissman. ‘‘While the LED general lighting market continues to grow, demand for LCD TVs has declined to their lowest levels since the global recession, according to industry analysts at IHS. This has resulted in excess supply of LEDs for the backlighting display market.’‘ Wafer sales have risen from $1.7m last quarter to $2.1m (roughly level on a year ago). Since revenue for polished wafers has fallen further from $1.8m a year ago and $0.84m last quarter to $0.76m, growth was due mainly to revenue for patterned sapphire substrates (PSS) rising again, from $0.26m a year ago and $0.9m last quarter to $1.4m. Optical and R&D revenues collectively were roughly level with last quarter at $1.35m (due mainly to optical revenue being down from $1.6m a year ago to $1.1-1.2m). ‘‘This market has also been relatively weak in recent quarters, but we are beginning to see some improvement,’‘ says chief financial officer Mardel Graffy. ‘‘We continue

to focus on this business and expect revenue from this market to grow in coming years,’‘ he adds. ‘‘The sapphire market remained very challenging in the third quarter as excess capacity in the market and fluctuations in inventory levels in the supply chain added additional downward pressure on pricing and volumes,’‘ comments Weissman. ‘‘The current oversupply in the sapphire industry has been driven by the anticipation of the mobile device market potentially converting to the use of sapphire for cover glass in smartphones. While we believe there is a good chance for the use of sapphire in that application, the timing for adoption and scale of that adoption - if it occurs - is uncertain. If sapphire cover glass is adopted on a large-scale, industry analysts suggest that the current excess sapphire capacity will be rapidly absorbed and significant capacity increases will be needed to support that application. While we are taking steps to assure that Rubicon is positioned to participate in the sapphire cover glass market if that application is adopted, we are also taking the actions necessary to diversify the business to reduce volatility [making the company less susceptible to the pricing swings in the bulk sapphire market] and drive stronger margins over the long term,’‘ Weissman adds. ‘‘Our key initiatives toward that aim include aggressively pursuing our PSS potential, targeting high-margin optical applications and developing new products. Our goal is to focus on products that require more intellectual property to produce, like large-diameter PSS wafers produced entirely in-house and optical products.’‘ Meanwhile, in the near-term, Rubicon is focusing on cost reduction to reduce cash usage. Despite idled plant costs rising from $1.6m last quarter to $1.8m, total operating expenses were cut from $3.2m last quarter to $3m due to lower spending on reporting compliance (which last quarter included annual report costs). Net loss has been cut further, from $9.3m ($0.36 per share) a year ago and $8.6m ($0.33 per share) last quarter to $7.7m ($0.29 per share). Net cash used in operating activities was $1.9m, cut from $5.1m last quarter. During the quarter, cash and short-term investments fell from $36m to $34.1m (with no debt). However, these non-GAAP figures exclude a $900,000 accrual for the pending settlement of

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securities litigation, plus a non-cash charge of $39.6m for the impairment of long-lived assets. ‘‘Due to the protracted weakness in sapphire pricing, it was determined in the period that our long-lived assets [machinery, equipment, facilities etc] should be written down to current fair market value in accordance with generally accepted accounting principles,’‘ notes Graffy. During the quarter, inventory levels rose by $1m, due mainly to increased work in process (WiP) consisting primarily of boules and cores as a result of the lower core sales. In fourth-quarter 2015, Rubicon expects the market to be particularly challenging. Given the high inventory levels in the supply chain, demand for 2- and 4-inch cores is weak. At the current pricing, the firm hence plans to limit sales of those products during Q4 to allow time for inventory in the supply chain to clear. ‘‘While we expect the market to improve, it is difficult to predict the timing and want to avoid building excess inventory,’‘ says Graffy. Rubicon has hence scaled-back crystal growth production further (now operating at 40% of capacity). ‘‘We will re-evaluate throughout the remainder of the quarter and look for improvement in demand going into the New Year,’‘ he adds. In addition, Rubicon's key PSS customer has delayed the start of its volume purchase order by a quarter, from 1 October to 1 January (based on revised end-customer demand), reducing wafer revenue in Q4. ‘‘The relationship with our customer is strong, and we've agreed to produce PSS wafers for their consignment inventory, so they will be available as needed,’‘ says Graffy. Utilization at Rubicon's wafering operations in Malaysia hence increased with the additional PSS volume. ‘‘We continue to work on implementing the changes associated with the resource sharing agreement [with a leading sapphire polisher] that we announced last quarter,’‘ he notes. ‘‘Once the other party begins using a portion of the Malaysia facility, our utilization will increase further. However, some of the depreciation that is currently reflected in idled plant will continue on but will be classified differently,’‘ adds Graffy. ‘‘Given the current market conditions, the timing of their use of our facility is uncertain. We

continue to benefit from the knowledge transfer of their lower-cost polishing process, which was the main driver for entering into this agreement.’‘ For fourth-quarter 2015, Rubicon's revenue will hence likely be limited to $2-3m. Net loss per share will rise slightly to about $0.30, as the firm will be incurring the cost of producing PSS wafers in advance of recognizing revenue. ‘‘The sapphire market is very challenging at the moment, with weakness in all markets,’‘ notes Weissman. ‘‘We expect improvement in the first quarter of next year, based on our visibility of PSS wafers sales [for consignment], and we also believe the LED and mobile device supply chain inventories should come down and anticipate some improvement in demand for 2- and 4-inch core in the first quarter,’‘ he adds. ‘‘We are taking actions necessary to diversify the business to reduce volatility and drive stronger margins over the long term while putting intense focus on cost reduction to reduce cash usage in the short term,’‘ says Weissman. ‘‘Reducing the level of cash usage is a top priority, and we believe we will show sustainable improvements in cash flow starting early next year as wafer costs decline and we reduce inventory levels,’‘ says Graffy. ‘‘Additional improvement is expected later in the year by increasing optical revenue,’‘ he adds. ‘‘However, given the expected inventory build in the current quarter for the wafer consignment inventory and limited core sales, cash used will be higher in the fourth quarter [back up to the $5m range]… but obviously we expect cash burn to be significantly lower than that going into next year,’‘ Graffy continues. ‘‘Our goal is to drive growth that is more balanced between large-diameter PSS, optical products, bulk crystal like cores and rectangular blocks, and new products,’‘ says Weissman. ‘‘The bulk crystal will likely continue to be volatile but has significant potential upside if the cover glass application is adopted. The rest of the business should offer good growth opportunities with less volatility and with good margins. Read more

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PATENT APPLICATION

More than 130 new patent applications were published between 2015-11-02 and 2015-12-01.

Patent Applicants Number of

new patent applications

Xiangneng Hualei Optoelectronic Corppration 8

Southeast University (Nanjing China) 6

Seoul Viosys 5

Xidian University 4

Ngk Insulators 4

Sanan Optoelectronics 4

Furukawa 4

Sharp 3

Denso 3 Other patent applicants: 13th Research Institute of China Electronics Technology, 5th Electronic Research Institute of Miit, Arizona State University, Beijing NMC, Beijing Yanyuan Sino Nitride Semiconductor Engineering Research Dev, Cambridge Electronics, Changchun Applied Chemistry, China Jiliang University, CNRS - Centre National Recherche Scientifique, Comba Telecom System, Covalent Materials, Doowon Electronics, Enraytek Optoelectronics, Epistar, Fudan University, Fujitsu, Guangdong University Of Technology, HC Semitek, Hefei Irico Epilight Technology, Hong Kong University of Science and Technology, HRL Laboratories, IBM, Industry Academy Cooperation Corps of Sunchon National University, Institute of Semiconductors (China), Intermolecular, Korea Photonics Technology Institute, Kyungpook National University Industry Academic Cooperation Foundatio, LG Innotek, Lightwave, Lumistal, Mitsubishi Chemical, Mitsubishi Electric, Nagoya Institute of Technology, Nagoya University, Nantong Tongfang Semiconductor, National Sun Yat-Sen University, NTT, Nisshin Kagaku, No55 Institute of China Electronics Science & Technology, No724 Institute of China Shipbuilding Industry, NXP, Optical Sciences, Osram Opto Semiconductors, Panasonic, Renesas Electronics, Research Center for Eco Environmental Sciences Chinese Academy of Sci., Robert Bosch, Rohm, Royal Institution for The Advancement of Learning Mcgill University, Saiokusu, Samsung Electronics, Semiconductor Components Industries, Seoul Semiconductor, Shanghai Huali Microelectronics, Shanghai Simgui Technology, Sixpoint Materials, South China University of Technology, Southwest Jiaotong University, Sumitomo Electric Industries, Suzhou Nanowin Science & Technology, Tamura Seisakusho, Tokuyama, Toyota Central Research & Development Labs, Tsinghua Tongfang, University Beijing, University of California, University of Xiamen …

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New patent applications selected by Knowmade Method for manufacturing a semiconductor material including a semi-polar iii-nitride layer Publ. Nb: WO2015177220 Patent Applicant: CNRS - Centre National Recherche Scientifique (FR)

uThe present invention relates to a method for manufacturing a semiconductor material including a semi-polar III-nitride layer, from a semi-polar starting substrate including a plurality of grooves periodically spaced apart. Each groove includes a first inclined flank having a crystallographic orientation C (0001) and a second inclined flank having a different crystallographic orientation. The method includes the phases which involve: forming (2) III-nitride crystals on the first inclined flanks of the grooves, the growth parameters of the III-nitride crystals being suitable for promoting lateral growth of said crystals such as to induce overlap of the adjacent III-nitride crystals, and continuing the growth until coalescence of the III-nitride crystals such as to form a layer of coalesced III-nitride crystals; and forming (3) a two-dimensional III-nitride layer on the layer of coalesced III-nitride crystals. Read more Group III nitride integration with cmos technology Publ. Nb: US2015318276, US2015318283 Patent Applicant: IBM (US)

A method of forming a structure that can be used to integrate Si-based devices, i.e., nFETs and pFETs, with Group III nitride-based devices is provided. The method includes providing a substrate containing an nFET device region, a pFET device region and a Group III nitride device region, wherein the substrate includes a topmost silicon layer and a <111> silicon layer located beneath the topmost silicon layer. Next, a trench is formed within the Group III nitride device region to expose a sub-surface of the <111> silicon layer. The trench is then partially filled with a Group III nitride base material, wherein the Group III nitride material base material has a topmost surface that is coplanar with, or below, a topmost surface of the topmost silicon layer. Read more Light-emitting diode and method for producing a light-emitting diode Publ. Nb: WO2015169585 Patent Applicant: Bosch (DE)

The invention relates to a light-emitting diode for the UVC spectral range, comprising a first aluminium (gallium) nitride layer (11) formed on a substrate (10), said first aluminium (gallium) nitride layer (11) being patterned using epitaxial lateral overgrowth by means of a mask being

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applied to the aluminium (gallium) nitride layer (11), the aluminium (gallium) nitride layer (11) being etched and the mask being removed, a second aluminium (gallium) nitride layer (14), which is grown onto the patterned first aluminium (gallium) nitride layer (11), and n-type ohmic contacts on the second aluminium (gallium) nitride layer (14), which are formed from vanadium/aluminium or titanium/aluminium. The invention furthermore relates to a corresponding method for producing a light-emitting diode. Read more Light modulators and digital exposure apparatuses including the same Publ. Nb: US2015323816, KR20150127492 Patent Applicant: Samsung Electronics (KR)

A light modulator may include: a light modulating unit formed as a pixel-array type by using a PIN diode including multiple quantum wells including a Group-III nitride semiconductor material, and configured to modulate light by electroabsorption; and/or a control unit including a transistor configured to control voltage applied to the PIN diode of the

light modulating unit. The PIN diode and the transistor may be arrayed in an active matrix form. Read more A multiple-coupled single photon emitters and a manufacturing method Publ. Nb: CN105048284 Patent Applicant: Sanan Optoelectronics (CN)

The present invention discloses a multi-coupled single photon light emitter and a manufacturing method thereof, are set on the top and bottom of making a multi-layer gallium nitride tapered pyramid quantum dots and Ag nanoparticles InGaN, using the quantum size effects of quantum structure, a single photon quantum InGaN exit point is achieved with the Ag nanoparticle plasmons surface of multiple quantum coupling, single-photon lasing is formed, thereby achieving high efficiency and high-strength single-photon emission.

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